Promoters Exhibiting Endothelial Cell Specificity and Methods of Using Same for Regulation of Angiogenesis

ABSTRACT

Isolated polynucleotide sequences exhibiting endothelial cell specific promoter activity, novel cis regulatory elements and methods of use thereof enabling treatment of diseases characterized by aberrant neovascularization or cell growth are disclosed.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/018,447 filed Feb. 1, 2011, which is a divisional of pending U.S.patent application Ser. No. 10/988,487 filed Nov. 14, 2004, which is acontinuation-in-part (CIP) of U.S. patent application Ser. No.10/135,447 filed May 1, 2002, now U.S. Pat. No. 7,067,649, which is acontinuation-in-part (CIP) of PCT Patent Application No. PCT/IL01/01059filed Nov. 15, 2001, which claims the benefit of priority of U.S.Provisional Patent Application No. 60/248,582 filed Nov. 17, 2000.

U.S. patent application Ser. No. 10/988,487 is also acontinuation-in-part (CIP) of U.S. patent application Ser. No.10/490,746 filed Apr. 12, 2004, now U.S. Pat. No. 7,585,666, which is aNational Phase of PCT Patent Application No. PCT/IL02/00339 filed May 1,2002, which claims the benefit of priority of U.S. Provisional PatentApplication No. 60/330,118 filed Oct. 19, 2001.

The contents of the above applications are incorporated herein byreference in their entirety.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to nucleic acid constructs, pharmaceuticalcompositions and methods which can be used to regulate angiogenesis inspecific tissue regions of a subject. More particularly, the presentinvention relates to isolated polynucleotide sequences exhibitingendothelial cell specific promoter activity, and methods of use thereofand, yet more particularly, to a modified-preproendothelin-1 (PPE-1)promoter which exhibits increased activity and specificity inendothelial cells, and nucleic acid constructs, which can be used toeither activate cytotoxicity in specific cell subsets, thus, enablingtreatment of diseases characterized by aberrant neovascularization orcell growth or induce the growth of new blood vessels, thus, enablingtreatment of ischemic diseases. The invention further relates tomodifications of the PPE promoter, which enhance its expression inresponse to physiological conditions including hypoxia and angiogenesis,and novel angiogenic endothelial-specific combined therapies.

Angiogenesis:

Angiogenesis is the growth of new blood vessels, a process that dependsmainly on locomotion, proliferation, and tube formation by capillaryendothelial cells. During angiogenesis, endothelial cells emerge fromtheir quiescent state and proliferate rapidly. Although the molecularmechanisms responsible for transition of a cell to angiogenic phenotypeare not known, the sequence of events leading to the formation of newvessels has been well documented [Hanahan, D., Science 277, 48-50,(1997)]. The vascular growth entails either endothelial sprouting[Risau, W., Nature 386, 671-674, (1997)] or intussusceptions [Patan, S.,et al; Microvasc. Res. 51, 260-272, (1996)]. In the first pathway, thefollowing sequence of events may occur: (a) dissolution of the basementof the vessel, usually a post capillary venule, and the interstitialmatrix; (b) migration of endothelial cells toward the stimulus; (c)proliferation of endothelial cells trailing behind the leadingendothelial cell (s); (d) formation of lumen (canalization) in theendothelial array/sprout; (e) formation of branches and loops byconfluencial anastomoses of sprouts to permit blood flow; (f) investmentof the vessel with pericytes (i.e., periendothelial cells and smoothmuscle cells); and (g) formation of basement membrane around theimmature vessel. New vessels can also be formed via the second pathway:insertion of interstitial tissue columns into the lumen of preexistingvessels. The subsequent growth of these columns and their stabilizationresult in partitioning of the vessel lumen and remodeling of the localvascular network.

Angiogenesis occurs under conditions of low oxygen concentration(ischemia and tumor metastases etc.) and thus may be an importantenvironmental factor in neovascularization. The expression of severalgenes including erythropoietin, transferrin and its receptor, most ofglucose transport and glycolytic pathway genes, LDH, PDGF-BB,endothelin-1 (ET-1), VEGF and VEGF receptors is induced under hypoxicconditions by the specific binding of the Hypoxia Inducible Factor(HIF-1) to the Hypoxic Response Element (HRE) regulating thetranscription of these genes. Expression of these genes in response tohypoxic conditions enables the cell to function under low oxygenconditions.

The angiogenic process is regulated by angiogenic growth factorssecreted by tumor or normal cells as well as the composition of theextracellular matrix and by the activity of endothelial enzymes (Nicosiaand Ottinetti, 1990, Lab. Invest., 63, 115). During the initial stagesof angiogenesis, endothelial cell sprouts appear through gaps in thebasement membrane of pre-existing blood vessels (Nicosia and Ottinetti,1990, supra; Schoefl, 1963, Virehous Arch, Pathol. Anat. 337, 97-141;Ausprunk and Folkman, 1977, Microvasc. Res. 14, 53-65; Paku andPaweletz, 1991, Lab. Invest. 63, 334-346). As new vessels form, theirbasement membrane undergoes complex structural and compositional changesthat are believed to affect the angiogenic response (Nicosia, et. al.,1994, Exp Biology. 164, 197-206).

Angiogenesis and Pathology:

A variety of angiogenic factors govern the angiogenic process. It isunderstood that during pathology, the fine balance betweenpro-angiogenic factors and anti-angiogenic factors is disrupted, therebyeliciting nonself-limiting endothelial and periendothelialcell-proliferation. Although angiogenesis is a highly regulated processunder normal conditions, many diseases (characterized as “angiogenicdiseases”) are driven by persistent unregulated angiogenesis. In suchdisease states, unregulated angiogenesis can either cause a particulardisease directly or exacerbate an existing pathological condition. Forexample, ocular neovascularization has been implicated as the mostcommon cause of blindness and underlies the pathology of approximatelytwenty diseases of the eye. In certain previously existing conditionssuch as arthritis, newly formed capillary blood vessels invade thejoints and destroy cartilage. In diabetes, new capillaries formed in theretina invade the vitreous humor, causing bleeding and blindness. Untilrecently, the angiogenesis that occurs in diseases of ocularneovascularization, arthritis, skin diseases, and tumors, had beendifficult to suppress therapeutically.

Unbalanced angiogenesis typifies various pathological conditions andoften sustains progression of the pathological state. For example, insolid tumors, vascular endothelial cells divide about 35 times morerapidly than those in normal tissues (Denekamp and Hobson, 1982 Br. J.Cancer 46:711-20). Such abnormal proliferation is necessary for tumorgrowth and metastasis (Folkman, 1986 Cancer Res. 46:467-73).

Vascular endothelial cell proliferation is also important in chronicinflammatory diseases such as rheumatoid arthritis, psoriasis andsynovitis, where these cells proliferate in response to growth factorsreleased within the inflammatory site (Brown & Weiss, 1988, Ann. Rheum.Dis. 47:881-5).

In atherosclerosis, formation of an atherosclerotic plaque is triggeredby a monoclonal expansion of endothelial cells in blood vessels(Alpern-Elran 1989, J. Neurosurg. 70:942-5). Furthermore, in diabeticretinopathy, blindness is thought to be caused by basement membranechanges in the eye, which stimulate uncontrolled angiogenesis andconsumption of the retina (West and Kumar, 1988, Lancet 1:715-6).

Endothelial cells are also involved in graft rejection. In allograftrejection episodes, endothelial cells express pro-adhesive determinantsthat direct leukocyte traffic to the site of the graft. It is believedthat the induction of leukocyte adhesion molecules on the endothelialcells in the graft may be induced by locally-released cytokines, as isknown to occur in an inflammatory lesion.

Abrogated angiogenesis, on the other hand, is also a major factor indisease development such as in atherosclerosis induced coronary arteryblockage (e.g., angina pectoris), in necrotic damage followingaccidental injury or surgery, or in gastrointestinal lesions such asulcers.

Hence, regulating or modifying the angiogenic process can have animportant therapeutic role in limiting the contributions of this processto pathological progression of an underlying disease state as well asproviding a valuable means of studying their etiology.

Recently significant progress in the development of endothelialregulating agents, whether designed to be inhibitory or stimulatory, hasbeen made. For example, administration of βFGF protein, within acollagen-coated matrix, placed in the peritoneal cavity of adult rats,resulted in a well-vascularized and normally perfused structure(Thompson, et al., PNAS 86:7928-7932, 1989). Injection of βFGF proteininto adult canine coronary arteries during coronary occlusion reportedlyled to decreased myocardial dysfunction, smaller myocardial infarctions,and increased vascularity (Yanagisawa-Miwa, et al., Science257:1401-1403, 1992). Similar results have been reported in animalmodels of myocardial ischemia using βFGF protein (Harada, et al., J ClinInvest 94:623-630, 1994, Unger, et al., Am J Physiol 266:H1588-H1595,1994).

However, for mass formation of long lasting functional blood vesselthere is a need for repeated or long term delivery of the abovedescribed protein factors, thus limiting their use in clinical settings.Furthermore, in addition to the high costs associated with theproduction of angiogenesis-regulating factors, efficient delivery ofthese factors requires the use of catheters to be placed in the coronaryarteries, which further increases the expense and difficulty oftreatment.

Therefore, the fundamental goal of all anti-angiogenic therapy is toreturn foci of proliferating microvessels to their normal resting state,and to prevent their regrowth [Cancer: Principles & Practice ofOncology, Fifth Edition, edited by Vincent T. DeVita, Jr, SamuelHellman, Steven A. Rosenberg. Lippincott-Raven Publishers, Philadelphia.(1997)]. Likewise, proangiogenic therapy is directed not only torestoring required angiogenic factors, but to reestablishing the properbalance between them (Dor, et al, Ann NY Acad Sci 2003; 995:208-16) (foran extensive review of pro- and antiangiogenic therapies see Zhang et alActa Bioch and Biophys Cinica, 2003:35:873-880, and Mariani et al.MedGenMed 2003, 5:22; and Folkman, Semin. Onc 2002, 29:15-18).

Antiangiogenic Therapy:

Anti-angiogenic therapy is a robust clinical approach, as it can delaythe progression of tumor growth (e.g., retinopathies, benign andmalignant angiogenic tumors).

In general, every disease caused by uncontrolled growth of capillaryblood vessels such as diabetic retinopathy, psoriasis, arthritis,hemangiomas, tumor growth and metastasis is a target for anti-angiogenictherapy.

For example, the progressive growth of solid tumors beyond clinicallyoccult sizes (e.g., a few mm³) requires the continuous formation of newblood vessels, a process known as tumor angiogenesis. Tumor growth andmetastasis are angiogenesis-dependent. A tumor must continuouslystimulate the growth of new capillary blood vessels to deliver nutrientsand oxygen for the tumor itself to grow. Therefore, either prevention oftumor angiogenesis or selective destruction of tumor's existing bloodvessels (vascular targeting therapy) underlies anti-angiogenic tumortherapy.

Recently, a plethora of anti-angiogenic agents has been developed forthe treatment of malignant diseases, some of which are already underclinical trials (for review see Herbst et al. (2002) Semin. Oncol.29:66-77, and Mariani et al, MedGenMed 2003; 5:22).

The most studied target for tumor anti-angiogenic treatment is thedominant process regulating angiogenesis in human i.e., the interactionof vascular endothelial growth factor (VEGF) with its receptor (VEGFR).Agents which regulate VEGFR pro-angiogenic action include (i) antibodiesdirected at the VEGF protein itself or to the receptor (e.g., rhuMAbVEGF, Avastin); (ii) small molecule compounds directed to the VEGFRtyrosine kinase (e.g., ZD6474 and SU5416); VEGFR targeted ribozymes.

Other novel angiogenesis inhibitors include 2-Methoxyestradiol (2-ME2) anatural metabolite of estradiol that possesses unique anti-tumor andanti-angiogenic properties and angiostatin and endostatin—proteolyticcleavage fragments of plasminogen and collagen XVIII, respectively.

Though promising in pre-clinical models, to date systemic administrationof all anti-angiogenic agents tested in clinical trials, have shownlimited rate of success and considerable toxicities includingthrombocytopenia, leukopenia and hemoptysis. These results suggest thatthere may be limits to the use of current tumor anti-angiogenic agentsas therapy for advanced malignancies. O'Reilly et al. have shown thatthe latency between the initiation of anti-angiogenic therapy andantitumor effect may result in initial tumor progression before responseto therapy [O'Reilly S et al. (1998) Proc Am Soc Clin Oncol 17:217a].Furthermore, recent studies suggest that the regulation of angiogenesismay differ among capillary beds, suggesting that anti-angiogenic therapymay need to be optimized on an organ/tissue-specific basis [Arap et al.(1998) Science 279:377-380].

Interestingly, poor results have also been obtained when anti-angiogenictherapy (e.g., heparin, heparin-peptide treatment) directed at smoothmuscle cell proliferation has been practiced on myocardial ischemia inpatients with coronary artery disease [Liu et al., Circulation, 79:1374-1387 (1989); Goldman et al., Atherosclerosis, 65: 215-225 (1987);Wolinsky et al., JACC, 15 (2): 475-481 (1990)]. Various limitationsassociated with the use of such agents for the treatment ofcardiovascular diseases included: (i) systemic toxicity creatingintolerable level of risk for patients with cardiovascular diseases;(ii) interference with vascular wound healing following surgery; (iii)possible damage to surrounding endothelium and/or other medial smoothmuscle cells.

Thus, these and other inherent obstacles associated with systemicadministration of anti-angiogenic factors (i.e., manufacturinglimitations based on in-vitro instability and high doses required; andpeak kinetics of bolus administration attributing to sub-optimaleffects) limit the effective use of angiogenic factors in treatingneo-vascularization associated diseases.

Anti-Angiogenic Gene Therapy for Cancer:

Tumor cell proliferation in primary tumors as well as in metastases isoffset by an increased rate of apoptosis due to a restricted supply ofnutrients. Dormant primary or metastatic tumors begin to developmetastases whenever an “angiogenic switch” occurs and nutrient supply isadequate for the size of the tumor.

An angiogenic switch may occur via several mechanisms:

1. Up-regulation of pro-angiogenic genes such as VEGF and bFGF byoncogenes, or down-regulation of angio-suppressors such asthrombospondin.

2. Activation of hypoxic inducible factor-1 (HIF-1) by tumor-relatedhypoxic conditions.

3. Pro-angiogenic protein secretion by tumor bed fibroblasts, which areinduced by tumor cells.

4. Bone marrow endothelial progenitors trafficking to the tumor.

TABLE 1 Endogenous regulators of tumor angiogenesis.

*Dose-dependent **Weak Angiogenic Activator

The relative balance between activators and inhibitors of angiogenesis(see Table 1 hereinabove) is important for maintaining tumors in aquiescent state. Reducing inhibitors or increasing activator levelsalters the balance and leads to tumor angiogenesis and tumor growth.

Oxygen diffusion to neoplastic tissue is inadequate when tumor tissuethickness exceeds 150-200 μm from the nearest vessel. So, by definition,all tumors that exceed these dimensions are already angiogenicallyswitched-on. The tumor cell proliferation rate is independent of thevascular supply. However, as soon as the angiogenic switch occurs, therate of apoptosis decreases by 3-4 fold (24). Furthermore, nutrientsupply and catabolite release are not the only contribution ofangiogenic vessels to the decline in tumor apoptosis. Microvasculatureendothelial cells also secrete anti-apoptotic factors, mitogens andsurvival factors such as b-FGF, HB-EGF, IL-6, G-CSF, IGF-1 and PDGF thatfurther suppress tumor cell apoptosis.

Tumor cells are genetically unstable due to high mutation rates, whichprovide them with an advantage over native cells. For example, mutationsin the p53 gene suppress the rate of apoptosis. Moreover, oncogenealteration of pro-angiogenic or angiogenic suppressor control (such asthe ras oncogene) may induce an angiogenic switch. However, a highmutation rate is not the only mechanism for cancer's geneticinstability. There is evidence of “apoptotic bodies” phagocytosed bytumor cells, resulting in aneuploidy and a further increase in geneticinstability. All in all, cancer relies on angiogenesis. Due to geneticinstability, cancer may orchestrate a pro-angiogenic cytokine balance,which suppresses its apoptotic rate and enables metastatic seeding.

The human vasculature system contains more than one trillion endothelialcells. The lifetime of normal quiescent endothelial cells exceeds 1000days. Although angiogenic endothelial cells involved in tumorprogression proliferate rapidly, they differ from tumor cells by theirgenomic stability, and thus also in minimal drug resistance and lowlikelihood of the development of mutant clones. Moreover, since therate-limiting factor for tumor progression is angiogenesis, treatmentdirected against angiogenic endothelial cells could yield highlyeffective treatment modalities. Indeed, several anti-angiogenicsubstances could serve as potential candidates for systemic therapy.However, since these agents are proteins and their administrationtherefore depends on frequent intravenous administration, their useposes serious manufacturing and maintenance difficulties. Delivery ofanti-angiogenic genes offers a potential solution for continuous proteinsecretion.

With the identification of new genes that regulate the angiogenicprocess, somatic gene therapy has been attempted to overcome theselimitations. Although, great efforts have been directed towardsdeveloping methods for gene therapy of cancer, cardiovascular andperipheral vascular diseases, there is still major obstacles toeffective and specific gene delivery [for review see, Feldman A L.(2000) Cancer 89(6):1181-94] In general, the main limiting factor ofgene therapy with a gene of interest, using a recombinant viral vectoras a shuttle is the ability to specifically direct the gene of interestto the target tissue.

Attempts to overcome these limitations included the use oftissue-specific promoters conjugated to cytotoxic genes. For example,endothelial cell targeting of a cytotoxic gene, expressed under thecontrol endothelial-specific promoters has been described by Jagger etal who used the KDR or E-selectin promoter to express TNFα specificallyin endothelial cells [Jaggar R T. Et al. Hum Gene Ther (1997)8(18):2239-47]. Ozaki et al used the von-Willebrand factor (vWF)promoter to deliver herpes simplex virus thymidine kinase (HSV-tk) toHUVEC [Hum Gene Ther (1996) 7(13):1483-90]. However, these promotersshowed only weak activity and did not allow for high levels ofexpression.

Several endothelial cell specific promoters have been described in theprior art. For example, Aird et al., [Proc. Natl. Acad. Sci. (1995)92:7567-571] isolated 5′ and to 3′ regulatory sequences of human vonWillebrand factor gene that may confer tissue specific expressionin-vivo. However, these sequences could mediate only a heterogeneouspattern of reporter transgene expression. Bacterial LacZ reporter geneplaced under the regulation of von Willebrand regulatory elements intransgenic mice revealed transgene expression in a subpopulation ofendothelial cells in the yolk sac and adult brain. However, noexpression was detected in the vascular beds of the spleen, lung, liver,kidney, heart, testes and aorta as well as in the thrombomodulin locus.

Korhonen J et al [Blood (1995) 96:1828-35] isolated the human and mouseTIE gene promoter which contributed to a homogeneous expression of atransgene throughout the vascular system of mouse embryos. However,expression in adult was limited to the vessels of the lung and kidneyand no expression was detected in the heart, brain, liver. Similarresults were obtained by Schlaeger M et al. who isolated a 1.2 kb 5′flanking region of the TIE-2 promoter, and showed transgene expressionlimited to endothelial cells of embryonic mice [Schlaeger T M et al.(1995) Development 121:1089-1098].

Thus, none of these sequences work uniformly in all endothelial cells ofall developmental stages or in the adult animal. Furthermore, some ofthese sequences were not restricted to the endothelium.

An alternate approach presented by Kong and Crystal included a tumorspecific expression of anti-angiogenic factors. To date, however, thetoxicity of recombinant forms of endogenous anti-angiogenic agents hasnot been demonstrated although some synthetic anti-angiogenic agentshave been associated with toxicity in preclinical models [Kong andCrystal (1998) J. Natl. Cancer Inst. 90:273-76].

Angiostatin has also been used as a possible anti-angiogenic agent(Folkman et al, Cell 1997 Jan. 24; 88(2):277-85), however due to theredundancy of factors involved in regulation of angiogenesis in tumors,it is highly unlikely that angiostatin therapy alone would be effective.

To date, promising clinical trials have shown that anti angiogenictreatments like Avastin® or Bay-43906®, can slow the metastaticprogression by limiting new growth of blood vessels surrounding thetumors. However, inhibiting the formation of new blood vessels and/orpartially destroying them may be insufficient in cancer pathologieswhere a dramatic anti angiogenic effect that destroys most or allexisting angiogenic blood vessels and induce tumor necrosis is required.

The Pre-Proendothelin-1 (PPE-1) Promoter

The endothelins (ET), which were discovered by Masaki et al. in 1988,consist of three genes: ET-1, ET-2 and ET-3. Endothelin-1 (ET-1), a 21amino acid peptide, was first described as a potent vasoconstrictor andsmooth muscle cell mitogen, synthesized by endothelial cells. ET-1 isexpressed in the vascular endothelium, although there is some expressionin other cells such as smooth muscle cells, the airways andgastrointestinal epithelium, neurons and glomerular mesangial cells. Itsexpression is induced under various pathophysiological conditions suchas hypoxia, cardiovascular diseases, inflammation, asthma, diabetes andcancer. Endothelin-1 triggers production and interacts with angiogenicfactors such as VEGF and PDGF and thus plays a role in the angiogenicprocess.

Hu et al. identified a hypoxia responsive element (HRE) that is locatedon the antisense strand of the endothelin-1 promoter. This element is ahypoxia-inducible factor-1 binding site that is required for positiveregulation of the endothelin-1 promoter (of the human, rat and murinegene) by hypoxia. Hypoxia is a potent signal, inducing the expression ofseveral genes including erythropoietin (Epo), VEGF, and variousglycolytic enzymes. The core sequence (8 base pairs) is conserved in allgenes that respond to hypoxic conditions and the flanking regions aredifferent from other genes. The ET-1 hypoxia responsive element islocated between the GATA-2 and the AP-1 binding sites.

Bu et al. identified a complex regulatory region in the murine PPE-1promoter (mET-1) that appears to confer endothelial cell specifictranscriptional activity and to bind proteins or protein complexes thatare restricted to the endothelial cell. This region, designatedendothelial specific positive transcription element, is composed of atleast three functional elements, positioned between the −364 bp and −320bp of the murine PPE-1 promoter. All three elements are required forfull activity. When one or three copies are constructed into a minimalmET-1 promoter, reporter gene expression in endothelial cells in vitroincreased 2-10 times, compared to a minimal promoter with no element.

U.S. Pat. No. 5,747,340 teaches use of the murine PPE-1 promoter andportions thereof. However, this patent neither implies nor demonstratesthat an endothelial-specific enhancer can be employed to increase thelevel of expression achieved with the PPE promoter while preservingendothelial specificity. Further, this patent does not teach that thePPE-1 promoter is induced to higher levels of transcription underhypoxic conditions.

Gene-Directed Enzyme Prodrug Therapy (GDEPT):

This strategy is also called “suicide gene therapy”. It involves theconversion of an inert prodrug into an active cytotoxic agent within thecancer cells. The two most widely used genes in GDEPT are herpes simplexvirus thymidine kinase (HSV-TK) coupled with ganciclovir (GCV)administration and the E. coli cytosine deaminase (CD) coupled with5-fluorocytosine (5FC) administration. The HSV-TK/GCV system hasundergone extensive preclinical evaluation, as well as clinical trials.To date, the HSV-TK/GCV system has demonstrated non-significant sideeffects such as fever, systemic toxicity of GCV, myelosuppression andmild-moderate hepatotoxicity.

The HSV-TK/GCV system was first described by Kraiselburd et al. in 1976.Cells transfected with an HSV-TK containing plasmid or transduced withan HSV-TK containing vector, are becoming sensitive for a super familyof drugs including aciclovir, ganciclovir (GCV), valciclovir andfamciclovir. The guanosine analog GCV is the most active drug in thesetup of gene therapy. HSV-TK positive cells produce a viral TK, whichis three orders of magnitude more efficient in phosphorylating GCV intoGCV monophosphate (GCV-MP) than the human TK. GCV-MP is subsequentlyphosphorylated by the native thymidine kinase into GCV diphosphate andfinally to GCV triphosphate (GCV-TP).

GCV-TP is a potent DNA polymerase inhibitor leading to termination ofDNA synthesis by incorporation into the nascent strand, terminating DNAelongation and eventually causing cell death. Since GCV affectspredominantly HSV-TK positive cells, its adverse effects are minimal andrare, and include mainly thrombocytopenia, neutropenia andnephrotoxicity. Moreover, since GCV toxicity is based on DNA synthesis,it affects mainly proliferating cells. The HSV-TK/GCV system hasrecently been utilized extensively in clinical trials of cancer genetherapy. Nevertheless, results are disappointing, mostly limited in vivoby a low transduction percentage.

Recent studies have characterized the HSV-TK/GCV cell cytotoxicitymechanism. They revealed cell cycle arrest in the late S or G2 phase dueto activation of the G2-M DNA damage checkpoint. These events were foundto lead to irreversible cell death as well as a bystander effect relatedto cell death. Profound cell enlargement is a well-known morphologicalchange in cells administered with the HSV-TK/GCV system. Thesemorphological changes are due to specific cytoskeleton rearrangement.Stress actin fibers and a net of thick intermediate filaments appearfollowing cell cycle arrest.

The HSV-TK/GCV system utilizes an amplification potential designated asthe “bystander effect”. The bystander effect stands for the phenomenonby which HSV-TK positive cells induce the killing of HSV-TK negativecells.

Bystander Effect:

The bystander effect was first described by Moolten et al., who foundthat a 1:9 mixture of HSV-TK positive and HSV-TK negative cells,respectively, results in complete cell killing following the addition ofGCV. Several characteristics of the bystander effect have beendescribed:

1. The bystander effect was found to be highly dependent on cell-cellcontact.

2. Its extent was different in different cell types.

3. It is not limited to homogenous cell types, but also to mixtures ofdifferent cell types.

4. Higher levels of HSV-TK expression were found to correlate with ahigher bystander effect.

Culver et al. were the first to demonstrate a bystander effect in an invivo model. They demonstrated tumor regression when implanted withHSV-TK positive tumor cells in different ratios. Unlike in vitro models,cell-cell contact was not found to be essential for the bystander effectin vivo. Kianmanesh et al. demonstrated a distant bystander effect byimplanting tumor cells in different liver lobes, where only some wereHSV-TK positive. Both HSV-TK positive and negative foci regressed. Abystander effect was also demonstrated in vivo between cells fromdifferent origins. All in all, HSV-TK and its bystander effectfacilitate an effective means for tumor suppression when implemented ingene delivery systems. However, to date, clinical studies havedemonstrated only limited results.

There is thus a widely recognized need for, and it would be highlyadvantageous to have highly specific, reliable angiogenic-specificpromoters and nucleic acid constructs providing a novel approach forefficiently regulating angiogenesis in specific tissue regions of asubject while being devoid of the toxic side effects and limited successcharacterizing prior art anti-angiogenesis approaches.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided anisolated polynucleotide comprising a cis regulatory element including atleast a portion of the sequence set forth in SEQ ID NO:15 covalentlylinked to at least a portion of the sequence set forth in SEQ ID NO:16,the isolated polynucleotide being capable of directing transcription ofa polynucleotide sequence transcriptionally linked thereto in eukaryoticcells. Also provided are nucleic acid constructs comprising the isolatedpolynucleotide, cells comprising the nucleic acid constructs of theinvention, and scaffolds seeded with the cells.

According to still further features in the described preferredembodiments the nucleic acid constructs further comprising a nucleicacid sequence positioned under the regulatory control of the cisregulatory element. The nucleic sequence can further encode anangiogenesis regulator.

According to still further features in the described preferredembodiments the nucleic acid sequence is selected from the groupconsisting of VEGF, p55, angiopoietin-1, bFGF and PDGF-BB.

According to yet further features in the described preferred embodimentsthe scaffold is composed of a synthetic polymer, a cell adhesionmolecule, or an extracellular matrix protein.

According to still further features in the described preferredembodiments the synthetic polymer is selected from the group consistingof polyethylene glycol (PEG), Hydroxyapatite (HA), polyglycolic acid(PGA), epsilon-caprolactone and 1-lactic acid reinforced with apoly-1-lactide knitted [KN-PCLA], woven fabric (WV-PCLA),interconnected-porous calcium hydroxyapatite ceramics (IP-CHA), polyD,L-lactic acid-polyethyleneglycol (PLA-PEG), unsaturated polyesterpoly(propylene glycol-co-fumaric acid) (PPF), polylactide-co-glycolide(PLAGA), polyhydroxyalkanoate (PHA), poly-4-hydroxybutyrate (P4HB), andpolyphosphazene.

According to yet further features in the described preferred embodimentsthe cell adhesion molecule is selected from the group consisting ofintegrin, intercellular adhesion molecule (ICAM) 1, N-CAM, cadherin,tenascin, gicerin, and nerve injury induced protein 2 (ninjurin2).

According to still further features in the described preferredembodiments the extracellular matrix protein is selected from the groupconsisting of fibrinogen, Collagen, fibronectin, vimentin,microtubule-associated protein 1D, Neurite outgrowth factor (NOF),bacterial cellulose (BC), laminin and gelatin.

According to yet another aspect of the present invention there isprovided a method of expressing a nucleic acid sequence of interest ineukaryotic cells, the method effected by administering to a subject anucleic acid construct including the nucleic acid sequence of interestpositioned under transcriptional control of a cis regulatory elementincluding at least a portion of the sequence set forth in SEQ ID NO:15covalently linked to at least a portion of the sequence set forth in SEQID NO:16.

According to still another aspect of the present invention there isprovided a method of regulating angiogenesis in a tissue, the methodeffected by expressing in the tissue a nucleic acid construct including:(a) an endothelial cell specific promoter; (b) at least one copy of ahypoxia response element set forth in SEQ ID NO:5; and (c) a nucleicacid sequence encoding an angiogenesis regulator, the nucleic acidsequence being under regulatory control of the promoter and the hypoxiaresponse element.

According to another aspect of the present invention there is provided amethod of regulating angiogenesis in a tissue, the method effected byexpressing in the tissue a nucleic acid construct including a nucleicacid sequence encoding an angiogenesis regulator, the nucleic acidsequence being under regulatory control of a cis regulatory elementincluding at least a portion of the sequence set forth in SEQ ID NO:15covalently linked to at least a portion of the sequence set forth in SEQID NO:16, thereby regulating angiogenesis in the tissue.

According to still further features in the described preferredembodiments, administering is effected by a method selected from thegroup consisting of, systemic in-vivo administration, ex-vivoadministration to cells removed from a body of a subject and subsequentreintroduction of the cells into the body of the subject; and localin-vivo administration.

According to yet further features in the described preferredembodiments, the tissue is a natural or an engineered tissue.

According to still further features in the described preferredembodiments the nucleic acid sequence encodes a proangiogenic factor andregulating angiogenesis is upregulating angiogenesis.

According to yet further features in the described preferred embodimentsthe nucleic acid sequence encodes an inhibitor of angiogenesis andregulating angiogenesis is downregulating angiogenesis.

According to yet another aspect of the present invention there isprovided a nucleic acid construct comprising: (a) a first polynucleotideregion encoding a chimeric polypeptide including a ligand binding domainfused to an effector domain of a cytotoxic molecule; and (b) a secondpolynucleotide region encoding a cis regulatory element being capable ofdirecting expression of said chimeric polypeptide in a specific tissueor cell. The ligand binding domain is selected such that it is capableof binding a ligand present in the specific tissue or cell, and bindingof said ligand to the ligand binding domain activates the effectordomain of the cytotoxic molecule. Also provided are eukaryotic cellstransformed with the nucleic acid construct of the invention.

According to yet further features in the described preferred embodimentsthe cis regulatory element is an endothelial cell-specific orperiendothelial cell-specific promoter selected from the groupconsisting of the PPE-1 promoter, the PPE-1-3× promoter, the TIE-1promoter, the TIE-2 promoter, the Endoglin promoter, the von Willerbandpromoter, the KDR/flk-1 promoter, The FLT-1 promoter, the Egr-1promoter, the ICAM-1 promoter, the VCAM-1 promoter, the PECAM-1 promoterand the aortic carboxypeptidase-like protein (ACLP) promoter.

According to further features in the described preferred embodiments theligand binding domain is a ligand-binding domain of a cell-surfacereceptor. The cell-surface receptor can be selected from the groupconsisting of a receptor tyrosine kinase, a receptor serine kinase, areceptor threonine kinase, a cell adhesion molecule and a phosphatasereceptor.

According to yet further features in the described preferred embodimentsthe cytotoxic molecule is selected from the group consisting of Fas,TNFR, and TRAIL.

According to yet another aspect of the present invention there isprovided method of downregulating angiogenesis in a tissue of a subject,the method effected by administering to the subject a nucleic acidconstruct designed and configured for generating cytotoxicity in asub-population of angiogenic cells. The nucleic acid construct includes:(a) a first polynucleotide region encoding a chimeric polypeptideincluding a ligand binding domain fused to an effector domain of acytotoxic molecule; and (b) a second polynucleotide region encoding acis regulatory element being for directing expression of the chimericpolypeptide in the sub-population of angiogenic cells. The ligandbinding domain is selected such that it is capable of binding a ligandpresent in, or provided to, the sub-population of angiogenic cells, andbinding of the ligand to the ligand binding domain activates theeffector domain of said cytotoxic molecule, thereby down-regulatingangiogenesis in the tissue.

According to still another aspect of the present invention there isprovided a method of down-regulating angiogenesis in a tissue of asubject, the method effected by: (a) expressing in the tissue of thesubject a nucleic acid construct designed and configured for generatingcytotoxicity in a sub-population of angiogenic cells, the nucleic acidconstruct including: (i) a first polynucleotide region encoding achimeric polypeptide including a ligand binding domain fused to aneffector domain of a cytotoxic molecule, wherein the effector domain isselected such that it is activated following binding of a ligand to theligand binding domain; and (ii) a second polynucleotide region encodinga cis acting regulatory element for directing expression of the chimericpolypeptide in the sub-population of angiogenic cells; and (b)administering to the subject the ligand, thereby down-regulatingangiogenesis in the tissue.

According to a further aspect of the present invention there is provideda pharmaceutical composition for down regulating angiogenesis in atissue of a subject including, as an active ingredient, a nucleic acidconstruct designed and configured for generating cytotoxicity in asubpopulation of angiogenic cells and a pharmaceutical acceptablecarrier. The nucleic acid construct includes: (a) a first polynucleotideto region encoding a chimeric polypeptide including a ligand bindingdomain fused to an effector domain of a cytotoxic molecule; and (b) asecond polynucleotide region encoding a cis regulatory element fordirecting expression of the chimeric polypeptide in the subpopulation ofangiogenic cells, wherein the ligand binding domain is selected capableof binding a ligand present in the specific tissue or cell, so that thebinding of the ligand to the ligand binding domain activates theeffector domain of the cytotoxic molecule.

According to yet a further aspect of the present invention there isprovided a method of treating a disease or condition associated withexcessive neo-vascularization. The method is effected by administering atherapeutically effective amount of a nucleic acid construct designedand configured for generating cytotoxicity in a sub-population ofangiogenic cells, the nucleic acid construct including: (i) a firstpolynucleotide region encoding a chimeric polypeptide including a ligandbinding domain fused to an effector domain of a cytotoxic molecule; and(ii) a second polynucleotide region encoding a cis acting regulatoryelement for directing expression of the chimeric polypeptide in thesub-population of angiogenic cells; and where the ligand binding domainis selected capable of binding a ligand present in, or provided to, thesub-population of angiogenic cells, and binding of the ligand to theligand binding domain activates the effector domain of the cytotoxicmolecule, thereby down-regulating angiogenesis in the tissue andtreating the disease or condition associated with excessiveneo-vascularization. Also provided is a method of treating a tumor in asubject, the method effected by administering a therapeuticallyeffective amount of the nucleic acid construct designed and configuredfor generating cytotoxicity in cells of the tumor.

According to still a further aspect of the present invention there isprovided a method of treating a disease or condition associated withischemia, the method effected by administering a therapeuticallyeffective amount of a nucleic acid construct designed and configured forgenerating angiogenesis in a sub-population of angiogenic cells, therebyup-regulating angiogenesis in the tissue and treating the disease orcondition associated with ischemia. The nucleic acid construct includes:(i) a first polynucleotide region encoding a proangiogenic factor; and(ii) a second polynucleotide region encoding a cis regulatory elementbeing for directing expression of the proangiogenic factor in asub-population of angiogenic cells.

According to further features in the described preferred embodiments,the disease or condition associated with ischemia is selected from thegroup consisting of wound healing, ischemic stroke, ischemic heartdisease and gastrointestinal lesions.

According to yet a further aspect of the present invention there isprovided a method of down-regulating angiogenesis in a tissue of asubject, the method effected by: (a) expressing in the tissue a nucleicacid construct designed and configured for cytotoxicity in angiogeniccells, the nucleic acid construct including: (i) a first polynucleotideregion encoding a suicide gene and (ii) a second polynucleotide regionencoding a cis acting regulatory element capable of directing expressionof the suicide gene in the angiogenic cells; and (b) administering tothe subject a therapeutic amount of a prodrug sufficient to causeapoptosis of the tissue when the prodrug is converted to a toxiccompound by the suicide gene, thereby down-regulating angiogenesis inthe tissue.

According to still a further aspect of the present invention there isprovided a pharmaceutical composition for down regulating angiogenesisin a tissue of a subject, the pharmaceutical composition including as anactive ingredient a nucleic acid construct designed and configured forgenerating cytotoxicity in angiogenic cells and a pharmaceuticalacceptable carrier. The nucleic acid construct includes: (a) a firstpolynucleotide region encoding a suicide gene, the suicide gene beingcapable of converting a prodrug to a toxic compound and (b) a secondpolynucleotide region encoding a cis acting regulatory element capableof directing expression of the suicide gene in the angiogenic cells.

According to yet another aspect of the present invention there isprovided a nucleic acid construct including: (a) a first polynucleotideregion encoding a suicide gene, the suicide gene being capable ofconverting a prodrug to a toxic compound, and (b) a secondpolynucleotide region encoding a cis regulatory element capable ofdirecting expression of the suicide gene in angiogenic cells. Alsoprovided are eukaryotic cells transformed with the nucleic acidconstruct of the invention.

According to yet a further aspect of the present invention there isprovided a method of down-regulating angiogenesis in a tissue of asubject, the method effected by administering to the subject a nucleicacid construct designed and configured for generating cytotoxicity inangiogenic cells. The nucleic acid construct includes: (a) a firstpolynucleotide region encoding a suicide gene; and (b) a secondpolynucleotide region encoding a cis regulatory element capable ofdirecting expression of the suicide gene in the angiogenic cells, wherethe suicide gene is selected capable of converting a prodrug to a toxiccompound capable of causing cytotoxicity, thereby down-regulatingangiogenesis in the tissue. According to still a further aspect of thepresent invention there is provided a method of treating a disease orcondition associated with excessive neo-vascularization, the methodeffected by administering a therapeutically effective amount of thenucleic acid construct of the invention designed and configured forcytotoxicity in angiogenic cells, thereby down-regulating angiogenesisin the tissue and treating the disease or condition associated withexcessive neo-vascularization.

According to still a further aspect of the present invention there isprovide a method of treating a tumor in a subject, the method effectedby administering a therapeutically effective amount of a nucleic acidconstruct designed and configured for generating cytotoxicity in cellsof the tumor, the nucleic acid construct including: (i) a firstpolynucleotide region encoding a suicide gene; and (ii) a secondpolynucleotide region encoding a cis acting regulatory element capableof directing expression of the suicide gene in the cells of the tumor,where the suicide gene is selected capable of converting a prodrug to atoxic compound capable of causing cytotoxicity in the cells of thetumor.

According to yet further features in the described preferred embodimentsthe suicide gene is selected from the group consisting of thymidinekinase of herpes simplex virus, thymidine kinase of varicella zostervirus and bacterial cytosine deaminase.

According to still further features in the described preferredembodiments the prodrug is selected from the group consisting ofganciclovir, acyclovir, 1-5-iodouracil FIAU, 5-fluorocytosine,6-methoxypurine arabinoside and their derivatives.

According to yet further features in the described preferred embodimentsthe suicide gene is thymidine kinase of herpes simplex virus and theprodrug is to ganciclovir, acyclovir, FIAU or their derivatives.

According to still further features in the described preferredembodiments the suicide gene is bacteria cytosine deaminase and saidprodrug is 5-fluorocytosine or its derivatives.

According to yet further features in the described preferred embodimentsthe suicide gene is varicella zoster virus thymidine kinase and saidprodrug is 6-methoxypurine arabinoside or its derivatives.

According to yet further features in the described preferred embodimentsthe method further comprises administering to the subject, incombination, at least one additional therapeutic modality, additionaltherapeutic modality selected capable of further potentiating saidcytotoxicity in a synergic manner. The at least one additionaltherapeutic modality can be selected from the group comprisingchemotherapy, radiotherapy, phototherapy and photodynamic therapy,surgery, nutritional therapy, ablative therapy, combined radiotherapyand chemotherapy, brachiotherapy, proton beam therapy, immunotherapy,cellular therapy and photon beam radiosurgical therapy.

According to further features in preferred embodiments of the inventiondescribed below, the nucleic acid sequence includes an isolatedpolynucleotide comprising a cis regulatory element including at least aportion of the sequence set forth in SEQ ID NO:15 covalently linked toat least a portion of the sequence set forth in SEQ ID NO:16, theisolated polynucleotide being capable of directing transcription of apolynucleotide sequence transcriptionally linked thereto in eukaryoticcells. The at least a portion of the sequence set forth in SEQ ID NO:15can be positioned upstream of the at least a portion of the sequence setforth in SEQ ID NO:16 in said cis regulatory element, or the least aportion of the sequence set forth in SEQ ID NO:16 can be positionedupstream of said at least a portion of the sequence set forth in SEQ IDNO:15.

According to still further features in the described preferredembodiments the cis regulatory element further includes at least onecopy of the sequence set forth in SEQ ID NO: 6, or at least two copiesof SEQ ID NO:6. The at least two copies of SEQ ID NO:6 can becontiguous.

According to yet further features in the described preferred embodimentsthe at least a portion of the sequence set forth in SEQ ID NO:15 iscovalently linked to the at least a portion of the sequence set forth inSEQ ID NO:16 via a linker polynucleotide sequence. The linkerpolynucleotide sequence can be a promoter and/or an enhancer element.

According to still further features in the described preferredembodiments the isolated polynucleotide includes at least one copy ofthe sequence set forth in SEQ ID NO: 1.

According to yet further features in the described preferred embodimentsthe isolated polynucleotide further includes a hypoxia response element,the hypoxia response element preferably including at least one copy ofthe sequence set forth in SEQ ID NO: 5.

According to still further features in the described preferredembodiments the cis regulatory element is as set forth in SEQ ID NO: 7.

According to still further features in the described preferredembodiments the nucleic acid construct further includes a conditionallyreplicating adenovirus.

According to yet further features in the described preferred embodimentsthe cis regulatory element is an endothelial cell-specific orperiendothelial cell-specific promoter selected from the groupconsisting of the PPE-1 promoter, the PPE-1-3× promoter, the TIE-1promoter, the TIE-2 promoter, the Endoglin promoter, the von Willerbandpromoter, the KDR/flk-1 promoter, The FLT-1 promoter, the Egr-1promoter, the ICAM-1 promoter, the VCAM-1 promoter, the PECAM-1 promoterand the aortic carboxypeptidase-like protein (ACLP) promoter.

The present invention successfully addresses the shortcomings of thepresently known configurations by providing isolated polynucleotidesequences comprising cis regulating elements with novel enhancerelements, and methods of use thereof. The novel enhancer elements can beused to make nucleic acid constructs and pharmaceutical compositions fortissue-specific regulation of transgene expression, and for treating avariety of disorders, diseases and conditions by gene therapy.Specifically, the cis regulatory elements, isolated polynucleotides andpharmaceutical compositions of the present invention can be used, alongwith selected transgenes, to specifically upregulate and/or downregulateangiogenesis in endothelial cells, thus treating tumors, metastaticdisease, and ischemic disease.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

The invention is herein described, by way of example only, withreference to the accompanying drawings. With specific reference now tothe drawings in detail, it is stressed that the particulars shown are byway of example and for purposes of illustrative discussion of thepreferred embodiments of the present invention only, and are presentedin the cause of providing what is believed to be the most useful andreadily understood description of the principles and conceptual aspectsof the invention. In this regard, no attempt is made to show structuraldetails of the invention in more detail than is necessary for afundamental understanding of the invention, the description taken withthe drawings making apparent to those skilled in the art how the severalforms of the invention may be embodied in practice.

In the drawings:

FIGS. 1 a-b are schematic illustrations of Fas chimera gene constructedfrom the extracellular region of TNFR1 and the trans-membrane andintracellular regions of Fas and cloned into pcDNA3 plasmid (a) or intoadenoviral vectors (b).

FIGS. 2 a-b illustrate apoptotic activity of the pro-apoptotic genes,Fas chimera and TNFR1. FIG. 2 a-illustrates Bovine Aortic EndothelialCells (BAEC) transfected with either pcDNA-3-TNFR1 (lower panel) orcontrol empty vector (upper panel) and an expression plasmid encodingGFP. FIG. 2 b—illustrates 293 Cells transfected with eitherpcDNA-3-Fas-c (lower panel) or control empty vector (upper panel) and anexpression plasmid encoding GFP. Transfected cells were visualized usingfluorescence microscopy and apoptotic activity was morphologicallydetermined.

FIGS. 3 a-f are electron microscopy images of BAEC cells transfectedwith pro-apoptotic genes. 24 hours post transfection, BAEC cells werefixed in 2.5% glutaraldehyde and processed. Presented are cells insuccessive stages of the apoptotic process.

FIG. 4 are histograms quantifying apoptotic activity of the indicatedpro-apoptotic genes in transfected BAEC and 293 cells.

FIG. 5 a represents a PCR analysis of AdPPE-Fas-c. Lanes 1-2—PCRproducts obtained using primers encompassing the PPE-1 promoter andFas-c gene. Lanes 3-4—PCR products obtained using Fas-c primers. Lanes5-6—PCR products obtained in the absence of template DNA.

FIG. 5 b is a western blot analysis of AdPPE-Fas-c transfected BAECcells. Protein samples were resolved by SDS-PAGE, transferred tonitrocellulose membrane and probed with a polyclonal antibody directedagainst the extracellular portion of TNFR1. Lane 1-2—pcDNA3-Fas-c BAECtransfected cells (positive control). Lane 3-4—BAEC cells transfectedwith the indicated MOI of AdPPE-Fas-c viruses. Lane 5—non-transfectedcells. Lane 6-7—BAEC cells transfected with the indicated MOI ofAdPPE-Luc.

FIGS. 6 a-d are photomicrographs illustrating the effect of Fas-chimeraover-expression on apoptosis of endothelial cells. BAEC cells wereinfected with: Ad-PPE-1-3×-Fas-chimera (FIG. 6 a);Ad-PPE-1-3×-luciferase (FIG. 6 b); Ad-PPE-1-3×-Fas-chimera andAd-PPE1-3×-GFP (FIG. 6 c); Ad-PPE-1-3×-luciferase and Ad-PPE-1-3×-GFP;each at MOI 1000 (FIG. 6 d). Photomicrographs were taken 72 h postinfection at ×10 magnification.

FIG. 7 is a histogram illustrating apoptotic specific effect ofAd-PPE-1-3×-Fas-chimera on endothelial cells. Viability of endothelial(BAEC, HUVEC) and non-endothelial (Normal skin fibroblasts-NSF) cellswas quantified by crystal violet staining 72 h post infection witheither Ad-PPE-1-3×-Fas-chimera or control (luciferase) virus.

FIG. 8 shows a dose response effect of TNFα administration onFas-chimera mediated apoptosis. BAEC were infected withAd-PPE-1-3×-Fas-c. 48 h post infection TNF was added to the growthmedium (at the indicated dose). Viability was determined by the crystalviolet assay 24 h thereafter.

FIGS. 9 a-e are photomicrographs illustrating an endothelialcell-specific apoptosis mediated by the cooperative action of TNFαligand and Fas-c receptor. The indicated cells were incubated in thepresence or absence of TNFα (10 ng/ml) 48 h following infection withAd-PPE-1-3×-Fas-c; crystal violet staining was effected 72 postinfection.

FIG. 10 a is a dose response curve illustrating the TNFα-dependentapoptotic effect of Ad-CMV-Fas-c on endothelial cells. Viability of BAECcells infected with the indicated MOI of Ad-CMV-Fas-chimera wasdetermined following incubation With TNFα.

FIGS. 10 b-d illustrate the apoptotic effect of TNFα ligand andAd-CMV-Fas-chimera on the non-endothelial cells NSF. FIG. 10 b—NSFinfected with a control virus. FIG. 10 c—NSF infected withAd-CMV-Fas-chimera. FIG. 10 d-NSF infected with Ad-CMV-Fas-chimera andincubated with TNF (10 ng/ml).

FIGS. 11 a-c illustrate the In-vivo anti-tumoral effect ofAd-PPE-1-3×-Fas-c. Mice inoculated with B16 melanoma cells were injectedintravenously with Ad-PPE-1-3×-Fas-c, Ad-CMV-Fas-chimera, control virusor saline when tumor was palpable.

FIG. 11 a—tumor areas, measured during treatment period. FIG. 11 b—tumorweights at end of treatment period. FIG. 11 c—an image representing thestate of the tumor in the Ad-PPE-1-3×-Fas-c treated mouse and thecontrol mouse.

FIG. 12 is a histogram illustrating the effect of the enhancer elementof the present invention on Luciferase expression in both bovine andhuman endothelial cell lines using the B2B cell line (bronchial cellline that expresses endothelin) as a control.

FIG. 13 is a histogram illustrating endothelial specificity of apromoter of the present invention in an adenoviral vector on Luciferaseexpression in various cell lines.

FIGS. 14A-B are photomicrographs illustrating GFP expression under thecontrol of Ad5PPE-1-3× of the present invention (14A) and an Ad5CMV(14B) control construct in the BAEC cell line.

FIG. 15 is histogram of % apoptosis induced by pACPPE-1-3×p55,pACPPE-1-3× Luciferase and pCCMVp55 in endothelial and non-endothelialcells.

FIG. 16 is a histogram illustrating the effect of introducing anenhancer element according to the present invention into a promoterconstruct on hypoxia response.

FIG. 17 is a histogram illustrating the effect of introducing anenhancer element according to the present invention into a promoter ofan adenovector construct on hypoxia response.

FIG. 18 is a histogram illustrating the effect of introducing anenhancer element according to the present invention into a promoter onlevels of expression in bovine and human endothelial, endothelinexpressing cell lines.

FIG. 19 is a histogram illustrating levels of expression of a reportergene observed in various organs following injection of an adenoviralconstruct containing either an endothelial promoter (PPE-1) or a control(CMV) promoter;

FIGS. 20A-B are two photomicrographs illustrating cellular expression ofan Ad5CMVGFP construct (FIG. 20A) and an Ad5PPE-1-GFP construct (FIG.20B) in liver tissue of mice injected with the constructs.

FIG. 21 is a histogram illustrating the effect of introducing anenhancer element according to the present invention into a promoter onlevels of expression in endothelial and non-endothelial cell lines.

FIG. 22 is a histogram illustrating the effect of introducing anenhancer element according to the present invention into a promoter onlevels of expression in endothelial and non-endothelial cell lines.

FIGS. 23A-C are photomicrographs illustrating GFP expression inAd5PPE-1-3×GFP transduced cells, Ad5PPE-1GFP transduced cells andAd5CMVGFP transduced cells respectively.

FIGS. 24A-13 illustrate GFP expression in SMC transduced by moi-1 ofAd5PPE-1-3×GFP and Ad5CMVGFP respectively.

FIGS. 25A-B show results of an experiment similar to that of FIGS. 24A-Bconducted in HeLa cells.

FIGS. 26A-B show results of an experiment similar to that of FIGS. 24A-Bconducted in HepG2 cells.

FIGS. 27A-B show results of an experiment similar to that of FIGS. 24A-B conducted in NSF cells.

FIGS. 28A-B are photomicrographs illustrating GFP expression inendothelial cells lining a blood vessel of mice injected with theAd5PPE-1GFP and the Ad5PPE-1-3×GFP constructs respectively.

FIGS. 29A-C are photomicrographs illustrating results from kidney tissueof injected mice. Ad5CMVGFP injected mice (FIG. 29A), Ad5PPE-1GFP (FIG.29B; slightly higher GFP expression is visible in the blood vessel wall;indicated by arrow) and Ad5PPE-1-3×GFP (FIG. 29C).

FIGS. 30A-C illustrate experiments similar to those depicted in FIGS.29A-C, is conducted on sections of spleen tissue.

FIGS. 31A-D illustrate GFP expression in metastatic lungs of controlmice injected with Saline (FIG. 31A), mice injected with Ad5CMVGFP (FIG.31 B), mice injected with Ad5PPE-1GFP (FIG. 31 C) and mice injected withAd5PPE-1-3×GFP (FIG. 31D). Anti Cd31 immunostaining (FIGS. 31C′ to 31D′)confirm the co-localization of the GFP expression and CD31 expression ineach metastatic tissue.

FIG. 32 is a histogram illustrating that Luciferase activity (lightunits/μg protein) in BAEC transfected by a plasmid containing the murinePPE-1 promoter is significantly higher when transfected cells wereincubated under hypoxic conditions.

FIG. 33 is a histogram as in FIG. 32, except that Ad5PPE-1Luc andAd5CMVLuc were employed.

FIG. 34 is a histogram as in FIG. 33 showing the effects of hypoxia indifferent cell lines.

FIG. 35 is a histogram illustrating the effect of the 3× sequence of thepresent invention on the PPE-1 hypoxia response in BAEC cells. Cellswere transduced by Ad5PPE-1Luc and Ad5PPE-1-3×Luc.

FIG. 36 is a histogram showing levels of Luciferase expression invarious tissues of PPE-1-Luc transgenic mice following femoral arteryligation.

FIGS. 37A-B are plasmid maps of constructs employed in conjunction withthe present invention.

FIGS. 38A-F illustrate the effects of Ad5PPE-1-3×VEGF and Ad5CMVVEGF onblood perfusion and angiogenesis in mouse ischemic limbs. FIGS. 38A-Dare representative ultrasonic (US) angiographic images of perfusion inthe ischemic limb of mice from the various treatment groups captured 21days following ligation. Yellow signal represents intense perfusion. Theright side of the image represents the distal end of the limb. FIG.38A—Ad5PPE-1-3×VEGF treated mouse; FIG. 38B—Ad5CMVVEGF treated mouse;FIG. 38C-control, saline treated mouse; FIG. 38D-control, normal limb.FIGS. 38E-F are histograms illustrating: mean intensity of signal in theUS images of the various treatment groups (FIG. 38E); mean capillarydensity, measured as the number of CD31+ cells/mm² in the varioustreatment groups (FIG. 38F).

FIG. 39 is a histogram illustrating Luciferase activity in proliferatingand quiescent Bovine Aortic Endothelial Cells (BAEC) transduced withAd5PPE-1Luc (open bars) and Ad5CMVLuc (black bars).

FIG. 40 is a histogram illustrating Luciferase activity in BAECtransduced with Ad5PPE-1Luc, during normal proliferation, a quiescentstate and rapid proliferation following addition of VEGF.

FIGS. 41A-B are histograms illustrating Luciferase activity (lightunits/μg protein) in the (FIG. 41A) aortas and livers (FIG. 41B) ofAd5PPE-1Luc and Ad5CMVLuc normal injected C57BL/6 mice. Activities weredetermined 1 (n=13), 5 (n=34), 14 (n=32), 30 (n=20) and 90 (n=11) dayspost injection.

FIGS. 42A-B are histograms illustrating relative Luciferase activity(light units/μg protein) detected five (FIG. 42A) and fourteen (FIG.42B) (n=10 for each time point) days post injection of Ad5PPE-1Luc (openbars) or Ad5CMVLuc (black bars) in normal injected BALB/C mice. Activityis expressed as percentage of total body Luciferase expression of eachanimal.

FIG. 43 is a prior art image depicting an aorta dissected from ApoEdeficient mice colored by Sudan—IV. The thoracic aorta contains less redstained atherosclerotic lesion while the abdominal region includes manyred stained atherosclerotic lesions. (Adapted from Imaging of Aorticatherosclerotic lesions by ¹²⁵I-HDL and ¹²⁵I-BSA. A. Shaish et al,Pathobiology 2001; 69:225-29).

FIG. 44 is a histogram illustrating absolute Luciferase activity (lightunits/μg protein) detected 5 days post systemic injections ofAd5PPE-1Luc (open bars; n=12) or Ad5CMVLuc (black bars; n=12) to ApoEdeficient mice. Luciferase activity observed from the abdominal aortacontain high lesion levels and from the thoracic area (low lesionlevels).

FIG. 45 is a histogram illustrating absolute Luciferase activity (lightunits/μg protein) 5 days post systemic injections of Ad5PPE-1Luc (blackbars) or Ad5CMVLuc (open bars) to healing wound C57BL/6 induced mice.

FIG. 46 is a histogram illustrating Luciferase activity in normal lung,metastatic lung and primary tumor of Lewis lung carcinoma-induced mice.Lewis lung carcinoma was induced by D122-96 cells injection to the backsfor primary tumor model and to the footpad for the metastatic model.Luciferase activity was measured five days post-systemic injection ofAd5PPE-1Luc (n=9; open bars) or Ad5CMVLuc (n=12; black bars). Activityis expressed as light units/μg protein.

FIGS. 47A-D are photomicrographs illustrating GFP expression and tissuemorphology in lungs and tumors of LLC bearing mice followingintra-tumoral injection of Ad5PPE-1GFP. Tissue was frozen in OCT andsectioned to 10 μm by cryostat. All pictures were taken in magnificationof 25×. FIG. 47A—GFP in angiogenic blood vessels of lung metastases;FIG. 47B—CD31 antibody immunostaining of the section pictured in FIG.47A; FIG. 47C—GFP expression in blood vessels of primary tumor; FIG.47D—phase contrast of the section of C illustrating blood vessels.

FIG. 48 is a histogram illustrating Luciferase expression in normal lungand metastatic lung of Lewis lung carcinoma-induced mice, injected withAdSCMVLuc, Ad5PPE-1Luc and Ad5PPE-1-3×-Luc Lewis lung carcinoma wasinduced by D122-96 cells injected to the foot pad for the metastaticmodel. Luciferase activity was measured five days post-systemicinjection of Ad5CMVLuc (n=7; black bars), Ad5PPE-1Luc (n=6; gray bars),or Ad5PPE-1-3×Luc (n=13; brown bars). Activity is expressed as lightunits/μg protein.

FIG. 49 is a histogram illustrating Luciferase activity as percentage ofliver activity (where the liver is 100%), in normal lung and lungmetastasis of Lewis lung carcinoma-induced mice injected with Ad5CMV,Ad5PPE-1Luc and Ad5PPE-1(3×).

FIGS. 50A-B are photomicrographs illustrating co-localization of GFPexpression (FIG. 50A) and CD31 immunostaining (FIG. 50B) in mice withLLC lung metastases injected with Ad5PPE-1-3×-GFP.

FIG. 51 is a histogram illustrating Luciferase activity (light units/μgprotein) in muscles (ischemic and normal) of PPE-1Luciferase transgenicmice at two, five, ten and 18 days post femoral ligation and in control(non-ligated animals—day 0; n=8 for each group).

FIG. 52 is a histogram illustrating Luciferase activity (light units/μgprotein) in the liver, lung and aorta in muscles (ischemic and normal)of PPE-1Luciferase transgenic mice at five (n=6), ten (n=6) and 18 (n=8)days post femoral ligation and in control (non ligated animals—day 0).

FIG. 53 is a histogram illustrating Luciferase activity, (light units/μgprotein detected in the livers, lungs and primary tumors of LLC miceinjected in primary tumors with Ad5CMVLuc (black bars) or Ad5PPE-1Luc(open bars).

FIGS. 54A-H are in-situ hybridization images illustrating tissuedistribution of tissue-specific or constitutive expression of varioustransgenes. FIGS. 54A-C illustrate in-situ hybridization with a VEGFspecific antisense probe on representative ischemic muscles from: A,Ad5PPE-1-3×VEGF treated mouse; B, Ad5CMVVEGF treated mouse; C, salinetreated mouse; D, liver section from Ad5CMVVEGF treated mouse. An arrowindicates positively stained cells. FIGS. 54E-G, illustrate in-situhybridization with a PDGF-B specific antisense probe of representativeischemic muscles from: E, Ad5PPE-1-3×PDGF-B treated mouse; F,Ad5CMVPDGF-B treated mouse; G, saline treated mouse; H, liver sectionfrom Ad5CMVPDGF-B treated mouse.

FIGS. 55A-B are histograms illustrating a long-term effect ofAd5PPE-1-3×VEGF or Ad5CMVVEGF on blood perfusion and angiogenesis inmouse ischemic limb. A, mean intensity of signal in the US images of thevarious treatment groups, 50 days following femoral artery ligation. B,mean capillary density, measured as number of CD31+ cells/mm² in thevarious treatment groups, 70 days following femoral artery ligation.

FIGS. 56A-D are histograms showing early and long term effects ofAd5PPE-1-3×PDGF-B on neovascularization in mouse ischemic limb. FIGS.56A-B—mean perfusion intensity measured by US imaging (56A, 30 daysfollowing femoral artery ligation; 56B, 80 days following femoral arteryligation). FIGS. 56C-D—mean capillary density, measured as number ofCD31+ cells/mm² in the various treatment groups (56C, 35 days followingfemoral artery ligation; 56D, 90 days following femoral arteryligation).

FIGS. 57A-G illustrate long term effects of angiogenic therapy usingPDGF-B and VEGF alone or in combination under regulation of anendothelial specific or a constitutive promoter on neovascularizationand blood flow in mouse ischemic limb. A, mean intensity of signal inthe US images of the various treatment groups, 80 days following femoralartery ligation. B, mean capillary density, measured as number of CD31+cells/mm² in the various treatment groups, 90 days following femoralartery ligation. FIGS. 57C-G—smooth muscle cells recruitment to maturevessels in ischemic limb muscles, 90 days following femoral arteryligation. Smooth muscle cells are immunostained with anti-α-SMactinantibodies (in red, ×20). C, Ad5PPE-1-3×PDGF-B treated mouse; D,combination therapy treated mouse; E, Ad5PPE-1-3×VEGF treated mouse; F,control, Ad5PPE-1-3×GFP treated mouse; G, normal contralateral limb(note that only large vessels are stained).

FIG. 58 illustrates the effect of PDGF-B alone or in combination withthe proangiogenic factor VEGF on blood perfusion in mouse ischemic limb50 days following artery ligation.

FIG. 59 is a schematic representation of the basic principles ofgene-directed enzyme prodrug therapy (GDEPT).

FIGS. 60A-B are a schematic map representing the construction of theplasmid pEL8(3×)-TK. FIG. 60A is a schematic map representing theconstruction of the plasmid pEL8(3×)-TK. FIG. 60B is a map of plasmidpACPPE-1(3×)-TK.

FIG. 61 is an agarose gel separation of PCR products of theAdPPE-1(3×)-TK vector, visualized by UV fluorescence. Two primers wereused: the forward primer 5′-ctcttgattcttgaactctg-3′ (455-474 bp in thepre-proendothelin promoter sequence) (SEQ ID NO:9) and the reverseprimer 5′-taaggcatgcccattgttat-3′ (1065-1084 bp in the HSV-TK genesequence) (SEQ ID NO:10). Primers specific for other vectors gave no PCRproducts. Note the 1 kb band, verifying the presence of the PPE-1(3×)promoter and the HSV-TK gene in the AdPPE-1(3×)-TK virus. Lane 1: 100 bpsize marker ladder. Lane 2: pACPPE-1(3×)-TK plasmid. Lane 3:AdPPE-1(3×)-TK virus. Lane 4. No DNA.

FIGS. 62A-C show linear, schematic maps of the vectors AdPPE-1(3×)-TKFIG. 62 a). AdPPE-1(3×)-Luc (FIG. 62 b) and AdCMV-TK (FIG. 62 c).

FIG. 63 is a series of photomicrographs illustrating the superiorendothelial in cell cytotoxicity of TK under control of the PPE-1 (3×)promoter. Bovine aorta endothelial cells (BAECs) were transduced withAdPPE-1(3×)-TK, AdCMV-TK and AdPPE-1(3×)-Luc multiplicity of infections(m.o.i.) of 0.1, 1, 10, 100, and 1000. GCV (1 μg/ml) was added fourhours post-transduction. Controls were cells transduced with the vectorswithout GCV, or GCV without vectors. The experiment was performed twicein 96-well plates, 12 wells for every group. Both controls did notinduce cell death (data not shown). Note the morphological changescharacteristic to cytotoxicity (cell enlargement, elongation andbloatedness) and cytotoxicity (loss of confluence) evident in AdPPE-1(3×)+GCV-treated cells, at a significantly lower m.o.i. than AdCMV-TK.Cells transduced with AdPPE-1 (3×)-Luc remained healthy (small size,rounded and confluent).

FIG. 64 is a graphic representation of endothelial cell cytotoxicity ofTK under control of the PPE-1 (3×) promoter. BAECs were prepared in96-well plates and transduced as in FIG. 13, followed by the addition of1 μg/ml GCV four hours post-transduction. 10 days post vector addition,cell viability was determined using crystal violet staining. Note thesuperior cytotoxicity of AdPPE-1 (3×)+GCV at high m.o.i.s.

FIG. 65 is a series of photomicrographs illustrating the superiorsynergy of endothelial cell cytotoxicity of TK under control of thePPE-1 (3×) promoter and ganciclovir administration. Bovine aortaendothelial cells (BAECs) were transduced with AdPPE-1(3×)-TK, AdCMV-TKand AdPPE-1(3×)-Luc, as described hereinabove, at multiplicity ofinfection (m.o.i.) of 10, and exposed to increasing concentrations ofGCV (0.001-10 μg/ml, as indicated), added four hours post-transduction.Controls were cells transduced with the vectors without GCV, or GCVwithout vectors. The experiment was performed twice in 96-well plates,12 wells for every group. Both controls did not induce cell death (datanot shown). Note the morphological changes characteristic tocytotoxicity (cell enlargement, elongation and bloatedness) andcytotoxicity (loss of confluence) evident in AdPPE-1 (3×)+GCV-treatedcells, at a significantly lower concentration of GCV than cells exposedto AdCMV-TK.

FIG. 66 is a graph representing synergy of endothelial cell cytotoxicityof TK under control of the PPE-1 (3×) promoter and gancicloviradministration. BAECs were prepared in 96-well plates and transduced asin FIG. 65, followed by the addition of increasing concentrations(0.0001-10 μg/ml) GCV four hours post-transduction. 10 days post vectoraddition, cell viability was determined using crystal violet staining.Note the superior cytotoxicity of AdPPE-1 (3×)+GCV at GCV concentrationsgreater than 0.01 μg/ml, compared with the strong constitutive TKexpression of AdCMV-TK.

FIG. 67 is a series of photomicrographs illustrating the specific,synergic endothelial cytotoxicity of TK under control of the PPE-1 (3×)promoter and ganciclovir administration. Endothelial [Bovine aorticendothelial cells (BAEC), Human umbilical vein endothelial cells(HUVEC)] and non-endothelial [Human hepatoma cells (HepG-2), Humannormal skin fibroblasts (NSF)] cells were transduced withAdPPE-1(3×)-TK, AdPPE-1(3×)-Luc or AdCMV-TK at m.o.i. of 10, followed bythe administration of 1 μg/ml GCV four hours post-transduction. Theexperiment was performed twice, in 96-well plates, 12 wells for everygroup. Cytotoxicity and cell morphological changes were detectedmicroscopically four days post-transduction. Note the superior cytotoxiceffect of AdPPE-1(3×)-TK,+GCV in the BAEC and HUVEC cultures[morphological changes characteristic to cytotoxicity (cell enlargement,elongation and bloatedness) and cytotoxicity (loss of confluence)], andthe absence thereof in HepG-2 and NSF cultures (cells remained small,rounded and confluent). AdPPE-1(3×)-Luc+GCV were nontoxic to all celltypes.

FIG. 68 is a histogram representing the specific, synergic endothelialcell cytotoxicity of TK under control of the PPE-1 (3×) promoter andganciclovir administration. Endothelial (BAEC and HUVEC) andnon-endothelial (HepG-2 and NSF) cells were prepared in 96-well platesand transduced as in FIG. 67, followed by the addition of increasingconcentrations (1 μg/ml) GCV four hours post-transduction. 10 days postvector addition, cell viability was determined using crystal violetstaining. Note the superior, endothelial specific cytotoxicity ofAdPPE-1 (3×)+GCV, compared with the non-specific cytotoxicity ofAdCMV-TK+GCV.

FIG. 69 is a series of photomicrographs illustrating the endothelialselective cytotoxicity of TK under control of the PPE-1 (3×) promoterand ganciclovir administration at extreme multiplicity of infection.Non-endothelial (NSF) cells were transduced with AdPPE-1(3×)-TK,AdPPE-1(3×)-Luc or AdCMV-TK as in FIG. 66, at the higher m.o.i. of 100,followed by the administration of 1 μg/ml GCV four hourspost-transduction. The experiment was performed twice, in 96-wellplates, 12 wells for every group. Cytotoxicity and cell morphologicalchanges were detected microscopically four days post-transduction. Notethe lack of effect on NSF cell morphology with AdPPE-1(3×)-TK+GCV,compared to the non-specific cytotoxicity of AdCMV-TK+GCV.

FIG. 70 is a series of photographs illustrating synergic suppression ofmetastatic growth by in vivo expression of TK under control of the PPE-1(3×) promoter and ganciclovir (GCV) administration. Lung metastases ofLewis Lung Carcinoma (LLC) were induced in 14 weeks old male C57BL/6mice (n=77) by inoculation of LLC tumor cells into the left foot pad,which was amputated as soon as the primary tumor reached a size of 7 mm.5 days later, 10¹¹ PFUs of the adenoviral vectors [AdPPE-1(3×)-TK+GCV;AdCMV-TK+GCV; AdPPE-1(3×)-TK without GCV] were injected into the tailvein followed by 14 days of 100 mg/kg GCV injection. The mice weresacrificed on the 24^(th) day post vector injection, and lungs removedfor inspection and analysis. Control mice received saline and GCV. Notethe significantly reduced extent of metastatic spread in the lungs ofAdPPE-1 (3×)+GCV treated mice, compared to those from mice treated withAdCMV-TK+GCV, AdPPE-1 without GCV and GCV without adenovirus.

FIG. 71 is a histogram illustrating synergic suppression of metastaticgrowth by in vivo expression of TK under control of the PPE-1 (3×)promoter and ganciclovir (GCV) administration. Lung metastases wereinduced in C57BL/6 mice, and the mice treated with 10¹¹ PFUs of theadenoviral vectors [AdPPE-1(3×)-TK+GCV; AdCMV-TK+GCV; AdPPE-1(3×)-TKwithout GCV] and GCV (100 mg/kg) as described hereinabove. The mice weresacrificed on the 24^(th) day post vector injection, and lungs removedfor assessment of the lung metastases. Control mice received saline andGCV. Note the significant suppression of metastatic mass in AdPPE-1(3×)+GCV-treated mice, compared to metastatic mass in GCV-free (greaterthan 85%) and AdCMV-TK+GCV and saline+GCV controls (greater than 75%).

FIGS. 72 a-72 c are representative histopathology sections of lungmetastases, illustrating synergic suppression of metastatic pathology byin vivo expression of TK under control of the PPE-1 (3×) promoter andganciclovir (GCV) administration. Lung metastases were induced inC57BL/6 mice, and the mice treated with 10¹¹ PFUs of the adenoviralvectors [AdPPE-1(3×)-TK+GCV; AdCMV-TK+GCV; AdPPE-1(3×)-TK without GCV]and GCV (100 mg/kg), as described hereinabove. The mice were sacrificedon the 24^(th) day post vector injection, and lung metastatic tissue(FIGS. 72 a and 72 b) or lung tissue (FIG. 72 c) were sectioned andstained with hematoxylin and eosin. Note the massive central necrosisand numerous clusters of mononuclear infiltrates in metastases fromlungs with AdPPE-1 (3×)+GCV administration (FIGS. 72 a and 72 b).

FIGS. 73 a-73 b are representative histopathology sections of inducedLLC lung metastases stained with TUNEL and anti-caspase-3 of lungmetastases, illustrating synergic enhancement of tumor apoptosis by invivo expression of TK under control of the PPE-1 (3×) promoter andganciclovir (GCV) administration. Sections from LLC lung metastases,induced and prepared as described in FIGS. 71 a-71 b were fixed andembedded in paraffin, and assayed for indicators of apoptosis by thedeoxynucleotide transferase-mediated dUTP-nick end-labeling (TUNEL)assay using the Klenow-FragE1 (Oncogene, Cambridge, Mass.) (FIG. 73 a)and anti-caspase-3-specific immunohistopathology (73 b). Note theenhanced apoptosis in the lung metastases from the mice treated withintravenous AdPPE-1 (3×)-TK+GCV.

FIGS. 74 a and 74 b are representative histopathology sections ofinduced LLC lung metastases stained with TUNEL and anti-caspase-3 oflung metastases, illustrating the endothelial-specific, synergicenhancement of tumor apoptosis by in vivo expression of TK under controlof the PPE-1 (3×) promoter and ganciclovir (GCV) administration.Sections from LLC lung metastases, induced and prepared as described inFIGS. 73 a-73 b were fixed and embedded in paraffin, and assayed forindicators of apoptosis by the deoxynucleotide transferase-mediateddUTP-nick end-labeling (TUNEL) assay using the Klenow-FragE1 (Oncogene,Cambridge, Mass.) (FIG. 74 a) and anti-caspase-3-specificimmunohistopathology (74 b). Black arrows indicate erythrocytes, redarrows apoptotic endothelial cells, and white arrows apoptotic tumorcells. Note the enhanced apoptosis in the vascular (endothelial) regionsof the lung metastases from the mice treated with intravenous AdPPE-1(3×)-TK+GCV.

FIGS. 75 a-75 d are representative immunohistopathology sections oftissue from murine lung carcinoma, illustrating theendothelial-specific, synergic inhibition of angiogenesis by in vivoexpression of TK under control of the PPE-1 (3×) promoter andganciclovir (GCV) administration. Sections from LLC lung metastases(FIG. 75 a) livers (FIG. 75 c) and normal lung tissue (FIG. 75 b)induced and prepared as described in FIGS. 73 a-73 b were fixed andembedded in paraffin, and assayed for indicators of angiogenesis byanti-CD-31 immunofluorescence. Note the short, indistinct vessels andabsence of continuity or branching in lung metastases fromAdPPE-1(3×)-TK+GCV treated mice. FIG. 75 d is a histogram showing acomputer-based vascular density assessment (Image Pro-Plus, MediaCyberneticks Incorporated) of the lung metastases vascularization(angiogenesis). Left bar: AdPPE-1(3×)TK+GCV; right bar: AdPPE-1(3×)TK noGCV.

FIG. 76 is a representative histopathology section of tissue from murineliver, illustrating the absence of hepatotoxicity in in-vivo expressionof TK under control of the PPE-1 (3×) promoter and ganciclovir (GCV)administration. Sections from livers of mice bearing LLC lung metastasesinduced and prepared as described in FIGS. 73 a-73 b were fixed andembedded in paraffin, and stained with hematoxylin and eosin. Note theabsence of cytotoxic indicators in livers from mice treated withAdPPE-1-TK+GCV (3×) (left panel), compared to the profound cytotoxicityin the livers from mice treated with the constitutively expressedAdCMV-TK+GCV (right panel)

FIG. 77 depicts a RT-PCR analysis illustrating the organ-specificexpression of the expression of TK under control of the PPE-1 (3×)promoter and ganciclovir (GCV) administration. LLC lung metastases wereinduced and prepared in nine 15 week-old C57BL/6 male mice as describedin FIGS. 73 a-73 b. Adenovirus vectors [AdPPE-1 (3×)-TK and AdCMV-TK],and saline control were delivered intravenously 14 days post primarytumor removal. The mice were sacrificed 6 days post vector injection,and organs harvested. RNA of different organs was extracted, asdescribed hereinbelow, and PPE-1 (3×) and HSV-TK transcripts amplifiedby RT-PCR PCR with PPE-1(3×) promoter and HSV-TK gene primers. Note theendothelial-specific expression of TK under control of the PPE-1 (3×)promoter (center, bottom panel).

FIGS. 78 a and 78 b are graphs illustrating a range of sub-therapeuticand non-toxic irradiation in Balb/c murine colon carcinoma tumor model.20 Balb/c male mice aged 8 weeks inoculated with CT-2.6 colon carcinomacells into the left thigh and received local irradiation with 0, 5, 10,or 15 Gy under general anesthesia, when the tumor diameter had reached4-6 mm. For tumor volume (76 a), the tumor axis was calculated accordingto the formula V=π/6×α²×β (α is the short axis and β is the long axis).The 5 Gy dose induced only a partial, non-statistically significantdelay in tumor progression (FIG. 78 a), and no significant weight loss(FIG. 78 b).

FIGS. 79 a-79 g illustrate synergistic suppression of tumor growth inmurine colon carcinoma with combined sub-therapeutic radiotherapy andexpression of TK under control of the PPE-1 (3×) promoter andganciclovir (GCV) administration. 100 male Balb/C mice aged 8 weeks wereinoculated with CT-26 colon carcinoma tumor cells. As soon as the tumoraxis reached 4-6 mm, 10¹¹ PFUs of the viral vectors [AdPPE-1 (3×)-TK orAdCMV-TK] were injected intravenously into the tail vein followed by 14days of daily intraperitoneal GCV injection (100 mg/kg body weight),where indicated. 3 days post vector administration, the mice wereirradiated with a local 5 Gy dose. Tumor volume was assessed accordingto the formula V=π/6×α²×β (α is the short axis and β is the long axis).FIG. 79 a shows mean tumor volume±S.E. on day 14 post vector injection.FIG. 79 b shows mean tumor volume progression over time, in groupstreated with radiotherapy. FIG. 79 c shows mean tumor volume progressionover time, in AdPPE-1(3×)-TK+GCV treated mice. FIG. 79 d shows meantumor volume progression over time, in AdCMV-TK GCV treated mice. FIG.79 e shows mean tumor volume progression over time, in control salineGCV treated mice. FIG. 79 f shows mean tumor volume progression overtime, in AdPPE-1(3×)-TK treated mice without GCV. FIG. 79 g is arepresentative example of the gross pathology of the CT-26 primary tumorin Balb/C mice on the day of sacrifice. Note that radiotherapysignificantly potentiated only the angiogenic endothelial celltranscription-targeted vector, AdPPE-1(3×)-TK, compared to thenon-targeted vector, AdCMV-TK (p=0.04) (FIG. 79 c-79 f). Treatmentregimens with all virus vectors were ineffective without radiotherapy.

FIGS. 80 a-80 b are representative histopathology sections of primaryCT-26 tumor showing synergistic induction of tumor necrosis in murinecolon carcinoma with combined sub-therapeutic radiotherapy andexpression of TK under control of the PPE-1 (3×) promoter andganciclovir (GCV) administration. Sections from CT-26 colon carcinomatumors induced and prepared as described in FIGS. 79 a-79 g were fixedand embedded in paraffin, and stained with hematoxylin and eosin. Notethe to areas of necrosis (FIG. 80 a) and granulation tissue (FIG. 80 b)with combined AdPPE-1 (3×)+GCV+low dose radiotherapy.

FIGS. 81 a-81 b are representative histopathology sections of inducedprimary colon carcinoma tumors stained with TUNEL and anti-caspase-3,illustrating synergic enhancement of endothelial cell and tumorapoptosis by combined radiotherapy and in vivo expression of TK undercontrol of the PPE-1 (3×) promoter and ganciclovir (GCV) administration.Sections from CT-26 primary colon carcinoma tumors, induced and preparedas described in FIGS. 77 a-77 g were fixed and embedded in paraffin, andassayed for indicators of apoptosis by the deoxynucleotidetransferase-mediated dUTP-nick end-labeling (TUNEL) assay using theKlenow-FragE1 (Oncogene, Cambridge, Mass.) (FIG. 81 a) andanti-caspase-3-specific immunohistopathology (81 b). Note the massiveapoptosis (FIG. 81 a) and the caspase-3—positive endothelial cells (81b) in the tumors from the mice treated with combined radiotherapy andintravenous AdPPE-1 (3×)-TK+GCV.

FIG. 82 is representative histopathology sections of induced primarycolon carcinoma tumors stained with anti-caspase-3, illustratingsynergic enhancement of endothelial cell and tumor apoptosis by combinedradiotherapy and in vivo expression of TK under control of the PPE-1(3×) promoter and ganciclovir (GCV) administration. Sections from CT-26primary colon carcinoma tumors, induced and prepared as described inFIGS. 79 a-79 g were fixed and embedded in paraffin, and assayed forindicators of apoptosis by anti-caspase-3-specific immunohistopathology.Black arrow indicates erythrocytes; red arrow indicates apoptoticendothelial cell, and white arrow indicates apoptotic tumor cell. Notethe GCV-dependent apoptotic effect.

FIGS. 83 a and 83 b are representative histopathology sections of livertissue and induced primary colon carcinoma tumors stained withanti-CD-31, illustrating synergic enhancement of inhibition of tumorvascularization by combined radiotherapy and in vivo expression of TKunder control of the PPE-1 (3×) promoter and ganciclovir (GCV)administration. Sections from liver tissue (83 b) and CT-26 primarycolon carcinoma tumors (83 a), induced and prepared as described inFIGS. 79 a-79 g were fixed and embedded in paraffin, and reacted withendothelial-specific anti-CD-31 for immunohistopathology. Black arrowindicates erythrocytes; red arrow indicates apoptotic endothelial celland white arrow indicates apoptotic tumor cell. Note the extensivevascular disruption in the tumors from the mice treated with combinedradiotherapy and intravenous AdPPE-1 (3×)-TK+GCV (83 a) compared withthe normal vasculature in the liver cells (83 b).

FIG. 84 is representative histopathology sections of mouse liver tissueshowing tissue-specific cytotoxicity of radiotherapy and TK expressionunder control of the PPE-1 (3×) promoter and ganciclovir (GCV)administration. Sections from mouse livers exposed to a vectors (AdPPE-1(3×)-TK and AdCMV-TK) and GCV, alone and in combination, were fixed andembedded in paraffin, and stained with hematoxylin and eosin. Note thetypical mild hepatotoxicity with AdCMV-TK and ganciclovir (left panel),and the absence of vascular abnormalities in the AdPPE-1 (3×)-TK treatedliver (right panel).

FIGS. 85 a and 85 b are graphs illustrating a range of sub-therapeuticand non-toxic irradiation in C57Bl/6 lung carcinoma metastatic model. 35C57Bl/6 male mice aged 8 weeks were inoculated with Lewis Lung Carcinoma(LLC) cells into the left footpad and received irradiation into thechest wall with 0, 5, 10, or 15 Gy under general anesthesia, 8 daysfollowing removal of the primary tumor. Mice were sacrificed 28 dayspost tumor removal. Weight loss indicated metastatic disease. The 5 Gydose was neither therapeutic (FIG. 85 a) nor toxic (FIG. 85 b).

FIGS. 86 a-86 d illustrate synergistic suppression of metastatic diseasein murine lung carcinoma with combined sub-therapeutic radiotherapy andexpression of TK under control of the PPE-1 (3×) promoter andganciclovir (GCV) administration. 180 male Balb/C mice aged 8 weeks wereinoculated with LLC cells into the left footpad. The foot was amputatedunder general anesthesia as soon as the primary tumor developed. 5 dayspost amputation, 10¹⁰ PFUs of vector [AdPPE-1(3×)-TK or AdCMV-TK] wereinjected into the tail vein, followed by 14 days of dailyintraperitoneal injections of GCV (100 mg/kg). 3 days post vectorinjection, a single 5 Gy dose of radiotherapy aimed at the mouse's chestwall was administered under general anesthesia. FIG. 86 a shows survivalof irradiated, non-vector treated mice over 55 days. FIG. 86 b showssurvival of AdPPE-1(3×)-TK treated mice. FIG. 86 c shows survival ofAdCMV-TK treated mice. FIG. 86 d shows survival of saline treatedcontrol mice. Note that radiotherapy significantly potentiated only theangiogenic endothelial cell transcription-targeted vector,AdPPE-1(3×)-TK, compared to the non-targeted vector, AdCMV-TK (FIG. 86b-86 d). Treatment regimens with all virus vectors were ineffectivewithout radiotherapy.

FIGS. 87 a-87 c are a series of histograms showing endothelial cellcytotoxicity of Fas-c under control of CMV promoter. Bovine aorticendothelial cells (BAEC) were stained with crystal violet 72 hours aftertransduction with 100 (left), 1000 (right) and 10000 (left bottom) moi'sof CMV-FAS (dark) or CMV-LUC (gray, negative control), and 24 hoursafter the addition of human TNF-α ligand, in different concentrations.Note the reduced viability of BAE cells at high moi and TNF-αconcentrations.

FIG. 88 is a graph of plaque development showing enhanced spread ofviral replication in 293 cells with CMV-FAS (blue diamonds) compared toCMV-LUC (red squares). Titers of CsCl-banded stocks of CMV-FAS andCMV-LUC were determined by PFU assay, as described hereinbelow. Data isplotted as number of plaques seen on every 2-3 days of the plaque assayin log-scale.

FIGS. 89 a and 89 b is a series of photographs of 293 cell culturesillustrating the higher rate of cell-to-cell spread of virus infection(plaquing) with CMV-Fas-c as compared with CMV-luciferase. 4 days afterinfection, photographs of plaques from CMV-FAS (left) and CMV-LUC(right) with identical dilution, were taken. Plaques from CMV-FAS areclearly larger than those of CMV-LUC, indicating a higher rate of cellto cell spread, probably induced by apoptosis.

FIG. 90 is a histogram illustrating the specific, synergic endothelialcytotoxicity of Fas-c under control of the PPE-1 (3×) promoter anddoxorubicin administration. BAE cells were exposed to 100 nM ofDoxorubicin 48 hours after vector (PPE-1 (3×)-FAS) transduction (10³moi). Dox+PPE-fas=Doxorubicin+PPE-1 (3×)-Fas-c (orange); Dox=Doxorubucinalone (green); PPE-FAS=PPE-1 (3×)-FAS (red); no treatment=black. Cellswere stained with crystal violet 96 hours after vector transduction, andcell viability was assessed microscopically. Note the significantsynergy in endothelial cytotoxicity between AdPPE-1 (3×)-Fas-c anddoxorubicin.

FIGS. 91 a-91 b are a graphic representation illustrating superiorinduction of angiogenesis in engineered tissue constructs by VEGF underthe control of the endothelin (PPE-1 3×). Tissue engineered constructs(undisclosed procedure) were grown with or without VEGF supplementationto the medium (50 ng/ml). Parallel constructs were infected withAd5PPEC-1-3×VEGF viruses or control Ad5PPEC-1-3×GFP adenoviruses(control virus) (for 4 hours). Following 2 weeks in culture theconstructs were fixed, embedded, sectioned and stained. Vascularizationwas expressed as the number of vessels per mm², and the percentage ofarea of sections that was vascularized. FIG. 91 a shows that infectionof the cells with Ad5PPEC-1-3×VEGF has an inductive effect on number andsize of vessels-like structures formed in the engineered constructs.Note the dramatic increase (4-5×) in both parameters of vascularizationin the Ad5PPEC-1-3×VEGF-transduced tissue constructs (VEGF virus),compared to constructs exposed to VEGF to the medium (VEGF medium). FIG.91 b is a histogram of LUC luminescence intensity, illustrating thesuperior survival and vascularization of implanted tissue constructsgrown with cells infected with Ad5PPEC-1-3×VEGF, compared withAd5PPEC-1-3×GFP controls.

FIG. 92 is the wild-type murine PPE-1 promoter DNA sequence. Thepromoter contains the endogenous endothelial specific positivetranscriptional element (black italics), the NF-1 response element (pinkitalics), the GATA-2 element (red italics), the HIF-1 responsive element(blue italics), the AP-1 site (green italics), the CAAT signal (orangeitalics) and the TATA box (purple italics).

FIG. 93 is the sequence of the 3× fragment of the modified murinepre-proendothelin-1 promoter. The fragment contains 2 completeendothelial cell specific positive transcription elements (red) and twoportions that are located as inverted halves of the original sequence(blue): SEQ ID NO:15 (nucleotides from the 3′ portion of thetranscription elements SEQ ID NO: 6), and SEQ ID NO:16 (nucleotides fromthe 5′ portion of the transcription elements SEQ ID NO: 6).

FIG. 94 is a histogram illustrating the tissue specific,Bosentan-induced enhancement of expression of the LUC gene under controlof the PPE-1 (3×) promoter in transgenic mice.

FIGS. 95 a and 95 b are histograms illustrating the lack of host immuneresponse to transgenes expressed under control of the PPE-1(3×)promoter, measured by ELISA. Note the nonspecific anti-adenovectorresponse (FIG. 95 a), compared with the minimal anti TNF-R1 responseevoked in the PPE-1(3×) Fas-c treated mice (FIG. 95 b).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is of polynucleotide sequences exhibitingendothelial cell specific promoter activity, and methods of use thereof.More particularly, the present invention relates to amodified-preproendothelin-1 (PPE-1) promoter which exhibits increasedactivity and specificity in endothelial cells, and nucleic acidconstructs, which can be used to activate apoptosis in specific cellsubsets, thus, enabling treatment of diseases characterized by aberrantneovascularization or cell growth. The invention further relates tomodifications of the PPE promoter, which enhance its expression inresponse to physiological conditions including hypoxia and angiogenesis,and novel angiogenic endothelial-specific combined therapies.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not limited in its applicationto the details set forth in the following description or exemplified bythe Examples. The invention is capable of other embodiments or of beingpracticed or carried out in various ways. Also, it is to be understoodthat the phraseology and terminology employed herein is for the purposeof description and should not be regarded as limiting.

Unbalanced angiogenesis typifies various pathological conditions andoften sustains progression of the pathological state. For example, insolid tumors, vascular endothelial cells divide about 35 times morerapidly than those in normal tissues (Denekamp and Hobson, 1982 Br. J.Cancer 46:711-20). Such abnormal proliferation is necessary for tumorgrowth and metastasis (Folkman, 1986 Cancer Res. 46:467-73). Vascularendothelial cell proliferation is also important in chronic inflammatorydiseases such as rheumatoid arthritis, psoriasis and synovitis, wherethese cells proliferate in response to growth factors released withinthe inflammatory site (Brown & Weiss, 1988, Ann. Rheum. Dis. 47:881-5).On the other hand, in ischemic conditions such as cardiac ischemia,Peripheral Vascular Diseases, wound healing, burn scarring and of thesame, the induction of angiogenesis has an healing effect (Thompson, etal., PNAS 86:7928-7932, 1998) and thus will be beneficial.

Hence, regulating or modifying the angiogenic process can have animportant therapeutic role in limiting the contributions of this processto pathological progression of an underlying disease state, as well asproviding a valuable means of studying the etiology of such diseases.Recently significant progress in the development of endothelialregulating agents, whether designed to be inhibitory or stimulatory, hasbeen made (for a recent review, see Mariani et al GenMedGen 2003, 5:22).However, for pro angiogenic applications and mass formation of longlasting functional blood vessel there is a need for repeated or longterm delivery of the above described protein factors, thus limitingtheir use in clinical settings. Furthermore, in addition to the highcosts associated with the production of angiogenesis-regulating factors,efficient delivery of these factors requires the use of catheters to beplaced in the coronary arteries, which further increases the expense anddifficulty of treatment.

To date, promising clinical trials have shown that anti angiogenictreatments like Avastin® or Bay-43906®, can blunt the metastasisprogression by limiting new growth of blood vessels surrounding thetumors. However, inhibiting the formation of new blood vessels and/orpartially destroying them may be insufficient in cancer pathologieswhere a dramatic anti angiogenic effect that destroys most or allexisting angiogenic blood vessels and induce tumor necrosis is required.Further, although promising in pre-clinical models, to date systemicadministration of all anti-angiogenic agents tested in clinical trials,have shown limited rate of success and considerable toxicities includingthrombocytopenia, leukopenia and hemoptysis. Thus, endothelial-specifictargeting of therapeutic agents is essential to pro- and anti-angiogenictherapies. Endothelial specific promoters have been described in theart, examples include flk-1, Flt-1 Tie-2 VW factor, and endothelin-1(see U.S. Pat. Nos. 6,200,751 to Gu et al; 5,916,763 to Williams et al,and 5,747,340 to Harats et al, all of which are incorporated byreference herein). Endothelial cell targeting of a therapeutic gene,expressed under the control endothelial-specific promoters has also beendescribed in the art. For example, Jagger et al used the KDR orE-selectin promoter to express TNFα specifically in endothelial cells[Jaggar R T. Et al. Hum Gene Ther (1997) 8(18):2239-47] while Ozaki etal used the von-Willebrand factor (vWF) promoter to deliver herpessimplex virus thymidine kinase (HSV-tk) to HUVEC [Hum Gene Ther (1996)7(13):1483-90]. Although these promoters are considered endothelial cellspecific, studies have shown that many of these promoters areinefficient at directing expression to endothelial cells, lacked thestrict specificity required, showed only weak activity and did not allowfor high levels of expression.

One approach to the construction of more efficient and specificendothelial promoters for therapeutic use has been the identificationand inclusion of tissue specific enhancer elements. Enhancer elementsspecific to endothelial cells have previously been described, forexample, by Bu et al. (J. Biol Chem. (1997) 272(19): 32613-32622) whodemonstrated that three copies of the enhancer element of PPE-1(containing elements ETE-C, ETE-D, and ETE-E) endows promoter sequenceswith endothelial cell specificity in-vitro. However, no in-vivo utilityof the enhancer element could be demonstrated.

As clearly illustrated in the Example section hereinbelow, the presentinventors have proven the enhancer element to be suitable for use inin-vivo therapeutic applications. By creating a unique, modified,thrice-repeated (3×) enhancer element (SEQ ID NO: 7), and assessing it'sactivity in directing endothelial-specific gene expression in-vitro andin-vivo, the present inventors have further constructed a highly activeenhancer element comprising portions of the 3× enhancer element sequencein a novel, rearranged orientation. This modified enhancer elementexhibits enhanced specificity to proliferating endothelial cellsparticipating in angiogenesis, and negligible activity in normalendothelial cells in-vivo. Thus, the present inventors have, for thefirst time, identified portions of the enhancer element which, whenreconfigured, impart superior activity to nearby promoter sequences.

Thus, according to one aspect of the present invention, there isprovided an isolated polypeptide comprising a cis regulatory elementcapable of directing transcription of a polynucleotide sequencetranscriptionally linked hereto in eukaryotic cells. The isolatedpolynucleotide includes at least a portion of the sequence set forth inSEQ ID NO:15, covalently linked to at least a portion of the sequence asset forth in SEQ ID NO:16. In one preferred embodiment, the at least aportion of the sequence set forth in SEQ ID NO:15 is positioned upstreamof the at least a portion of the sequence set forth in SEQ ID NO:16 inthe cis regulatory element. In yet another preferred embodiment, the atleast a portion of the sequence set forth in SEQ ID NO:16 is positionedupstream of the at least a portion of the sequence set forth in SEQ IDNO:15 in the cis regulatory element.

SEQ ID NO:15 is a polynucleotide sequence representing nucleotidecoordinates 27 to 44 of the murine endothelial specific enhancer element(SEQ ID NO:6), with an additional guanyl nucleotide linked at the 3′terminus, and SEQ ID NO:16 is a polynucleotide sequence representingnucleotide coordinates 1 to 19 of the murine endothelial specificenhancer element (SEQ ID NO:6).

For purposes of this specification and the accompanying claims, the term“enhancer” refers to any polynucleotide sequence, which increases thetranscriptional activity of a promoter, preferably, but not exclusively,in a tissue specific manner. As used herein, the phrase “tissue specificenhancer” refers to an enhancer which increases the transcriptionalactivity of a promoter in a tissue- or context-dependent manner. It willbe appreciated that such a “tissue specific enhancer” reduces, inhibitsor even silences the transcriptional activity of a promoter innon-compatible tissue or environment.

According to some embodiments of the invention, the isolatedpolynucleotide includes contiguous copies of at least a portion of SEQID Nos: 15 and 16. Such sequences are preferably positioned in a head-totail orientation, although other orientations well known in the art canbe constructed, such as inverted orientation (tail to tail, or head tohead), complementary orientation (replacing “a” with “t”, “t” with “a”,“g” with “c”, and “c” with “g”), inverted complementary orientation, andthe like. The at least a portion of the sequence as set forth in SEQ IDNO:15 can be covalently linked directly to the at least a portion of thesequence as set forth in SEQ ID NO:16, or, in a preferred embodiment,the two sequences can be linked via a linker polynucleotide sequence. Asused herein, the term “linker polynucleotide” refers to a polynucleotidesequence which is linked between two or more flanking polynucleotides(e.g. SEQ ID Nos: 15 and 16). One such preferred linker sequence is thetrinucleotide sequence “cca”, for example, which is the linker sequenceas set forth in nucleotides in positions 55-57 of SEQ ID NO:7. Othersuitable linker sequences can include entire additional enhancerelements, native or artificial, for example, multiple copies of SEQ IDNO.15, SEQ ID NO:16, the 1× enhancer element of PPE-1, additional entirepromoters, hypoxia response element (such as SEQ ID NO: 5), and thelike.

As used herein, the phrase “a portion of the sequence as set forth inSEQ ID NO:15 . . . ” or “a portion of the sequence as set forth in SEQID NO:16 . . . ” is defined as a sequence representing at least 8contiguous nucleotides of the 5′ terminus, 3′ terminus or any sequencetherebetween, of the indicated sequence. Thus, for example, thesequences representing nucleotide coordinates 1-8, 1-9, 1-10, 1-11 . . ., in to increments of 1 nucleotide up to nucleotide coordinates 1-17 ofSEQ ID NO:15 all constitute a portion of SEQ ID NO:15 according to thepresent invention, as do all the sequences representing nucleotidecoordinates 2-9, 2-10, 2-11, . . . to 2-17 of SEQ ID NO:15, as do allthe sequences representing nucleotide coordinates 3-10, 3-11, 3-12, . .. to 3-17 of SEQ ID NO:15, inclusive up to sequences representingnucleotide coordinates 10-17 of SEQ ID NO:15. Similarly, the sequencesrepresenting nucleotide coordinates 1-8, 1-9, 1-10, 1-11 . . . , inincrements of 1 nucleotide up to nucleotide coordinates 1-19 of SEQ IDNO:16 all constitute a portion of SEQ ID NO:16 according to the presentinvention, as do the sequences representing nucleotide coordinates 2-9,2-10, . . . , as described hereinabove.

While reducing the present invention to practice, it was uncovered thatthe modified enhancer PPE-1(3×) includes a sequence as set forth in SEQID NO:15 linked to a sequence as set forth in SEQ ID NO:16, flankedImmediately upstream and immediately downstream by a copy of the murineendothelial specific enhancer element (1×) (see SEQ ID NO:7). Thus, inone preferred embodiment, the cis regulatory element of the presentinvention further includes at least one copy of the sequence as setforth in SEQ ID NO:6. In a more preferred embodiment, the cis regulatoryelement includes at least two copies of the sequence as set forth in SEQID NO:6. In a most preferred embodiment, the cis regulatory element ofthe present invention is as set forth in SEQ ID NO:7.

Preferably the isolated polynucleotide further includes an endothelialcell-specific promoter sequence element. For purposes of thisspecification and the accompanying claims, the term “promoter” refers toany polynucleotide sequence capable of mediating RNA transcription of adownstream sequence of interest. The endothelial specific promoterelement may include, for example, at least one copy of the PPE-1promoter. Examples of suitable promoters/enhancers which can be utilizedby the nucleic acid construct of the present invention include theendothelial-specific promoters: preproendothelin-1, PPE-1 promoter(Harats D, J Clin Invest. 1995 March; 95(3):1335-44)., the PPE-1-3×promoter [PCT/IL01/01059; Varda-Bloom N, Gene Ther 2001 June;8(11):819-27], the TIE-1 (S79347, S79346) and the 1′1E-2 (U53603)promoters [Sato T N, Proc Natl Acad Sci USA 1993 Oct. 15;90(20):9355-8], the Endoglin promoter [Y11653; Rius C, Blood 1998 Dec.15; 92(12):4677-90], the von Willebrand factor [AF152417; Collins C JProc Natl Acad Sci USA 1987 July; 84(13):4393-7], the KDR/flk-1 promoter[X89777, X89776; Ronicke V, Circ Res 1996 August; 79(2):277-85], TheFLT-1 promoter [D64016 AJ224863; Morishita K.: J Biol Chem 1995 Nov. 17;270(46):27948-53], the Egr-1 promoter [AJ245926; Sukhatme V P, OncogeneRes 1987 September-October; 1(4):343-55], the E-selectin promoter[Y12462; Collins T J Biol Chem 1991 February 5; 266(4):2466-73], Theendothelial adhesion molecules promoters: ICAM-1 X84737; Horley K J EMBOJ. 1989 October; 8(10):2889-96], VCAM-1 [M92431; Iademarco M F, J BiolChem 1992 Aug. 15; 267(23):16323-9], PECAM-1 [AJ313330 X96849; CD31,Newman P J, Science 1990 Mar. 9; 247(4947):1219-22], the vascularsmooth-muscle-specific elements: CArG box X53154 and aorticcarboxypeptidase-like protein (ACLP) promoter [AF332596; Layne M D, CircRes. 2002; 90: 728-736] and Aortic Preferentially Expressed Gene-1[Yen-Hsu Chen J. Biol. Chem., Vol. 276, Issue 50, 47658-47663, Dec. 14,2001]. Other suitable endothelial specific promoters are well known inthe art, such as, for example, the EPCR promoter (U.S. Pat. Nos.6,200,751 to Gu et al) and the VEGF promoter (U.S. Pat. No. 5,916,763 toWilliams et al).

It will be appreciate that other, non-endothelial promoters can also beincorporated into the isolated polynucleotide described above, in orderto direct expression of desired nucleic acid sequences in a variety oftissue. Promoters suitable for use with the construct of the presentinvention are well known in the art. These include, but are not limitedto viral promoters (e.g., retroviral ITRs, LTRs, immediate early viralpromoters (IEp) (such as herpesvirus IEp (e.g., ICP4-IEp and ICP0-IEp)and cytomegalovirus (CMV) IEp), and other viral promoters (e.g., lateviral promoters, latency-active promoters (LAPs), Rous Sarcoma Virus(RSV) promoters, and Murine Leukemia Virus (MLV) promoters)). Othersuitable promoters are eukaryotic promoters which contain enhancersequences (e.g., the rabbit .beta.-globin regulatory elements),constitutively active promoters (e.g., the .beta.-actin promoter, etc.),signal and/or tissue specific promoters (e.g., inducible and/orrepressible promoters, such as a promoter responsive to TNF or RU486,the metallothionine promoter, PSA promoter, etc.), and tumor-specificpromoters such as the telomerase, plastin and hexokinase promoters.

Preferably, the isolated polynucleotide further includes a hypoxiaresponse element, for example at least one copy of the sequence setforth in SEQ ID NO: 5.

The isolated nucleic acid sequence of the present invention can be usedto regulate gene expression in eukaryotic tissue, and in particular, inproliferating endothelial cells, for example endothelial cells involvedin angiogenesis, or for silencing (inhibiting) gene expression inresting endothelial cells.

Thus, the isolated polynucleotide sequence of the present invention maybe provided, in some cases, as part of a nucleic acid construct furtherincluding a nucleic acid sequence positioned under the regulatorycontrol of the isolated polynucleotide of the present invention. Thenucleic acid construct of the present invention can further includeadditional polynucleotide sequences such as for example, sequencesencoding selection markers or reporter polypeptides, sequences encodingorigin of replication in bacteria, sequences that allow for translationof several proteins from a single mRNA (IRES), sequences for genomicintegration of the promoter-chimeric polypeptide encoding region and/orsequences generally included in mammalian expression vector such aspcDNA3, pcDNA3.1(+/−), pZeoSV2(+/−), pSecTag2, pDisplay, pEF/myc/cyto,pCMV/myc/cyto, pCR3.1, which are available from Invitrogen, pCI which isavailable from Promega, pBK-RSV and pBK-CMV which are available fromStratagene, pTRES which is available from Clontech, and theirderivatives. Such a nucleic acid construct is preferably configured formammalian cell expression and can be of viral origin. Numerous examplesof nucleic acid constructs suitable for mammalian expression are knownin the art; the Examples section which follows provides further detailof several such constructs.

For purposes of this specification and the accompanying claims, thephrase “nucleic acid sequence positioned under regulatory control . . .” refers to any polynucleotide sequence that has the capacity to betranscribed by an RNA polymerase, which transcription thereof can bedirected by a cis regulatory element, such as the cis regulatory elementof the present invention. This definition includes coding sequencestranslatable into polypeptides, as well as sequence for antisense RNA,RNA which binds DNA, ribozymes and other molecular moieties which arenot destined to undergo translation. Examples of nucleic acid sequenceswhich may be used by the construct according to the present inventionare, for example, positive and negative regulators of angiogenesis suchas VEGF, FGF-2, PDGF, angiopoietin-1 and angiopoietin-2, TGF-β, IL-8(for an extensive list of regulators of angiogenesis, see Table 1hereinabove), cytotoxic drugs, reporter genes and the like. In apreferred embodiment, the nucleic acid sequence is selected from theangiogenesis regulators VEGF, p55, angiopoietin-1, bFGF and PDGF-BB.Additional transcribable nucleic acid sequences suitable for control bythe cis regulatory element of the present invention are providedhereinbelow and in the Examples section which follows.

Examples presented hereinbelow illustrate that the novel cis regulatoryelements of the present invention can reliably direct expression of areporter gene (GFP and LUC) to endothelial tissue following systemicin-vivo administration, in a preferential manner in ischemic and/orangiogenic (proliferating) endothelial tissue. More significantly, theexamples further show, that the isolated polynucleotide of the presentinvention can be used to preferentially express therapeutic genes intumors, metastases, ischemic and/or angiogenic tissue, thus providingdirect evidence as to the importance of the cis regulatory element ofthe present invention, and its derivatives, in therapeutic applications.

In one embodiment, the nucleic acid construct of the present inventionis used in upregulating angiogenesis in a tissue, and treating orpreventing a disease or condition associated with ischemia. Such diseaseand conditions, which would benefit from enhanced angiogenesis, are wellknown in the art, for example—wound healing, ischemic stroke, ischemicheart disease and gastrointestinal lesions.

As used herein, the phrase “down-regulating angiogenesis” refers toeither slowing down or stopping the angiogenic process, which lead toformation of new blood vessels. The phrase “upregulating angiogenesis”refers to enhancing the expression of a dormant or minimally-functioningendothelial cell angiogenesis activator.

Thus, the present invention can be used for gene therapy. Gene therapyas used herein refers to the transfer of genetic material (e.g. DNA orRNA) of interest into a host to treat or prevent a genetic or acquireddisease or condition or phenotype. The genetic material of interestencodes a product (e.g. a protein, polypeptide, peptide, functional RNA,antisense) whose production in vivo is desired. For example, the geneticmaterial of interest can encode a hormone, receptor, enzyme, polypeptideor peptide of therapeutic value. For review see, in general, the text“Gene Therapy” (Advanced in Pharmacology 40, Academic Press, 1997).

Two basic approaches to gene therapy have evolved: (1) ex vivo and (2)in vivo gene therapy. In ex vivo gene therapy cells are removed from apatient, and while being cultured are treated in vitro. Generally, afunctional replacement gene is introduced into the cell via anappropriate gene delivery vehicle/method (transfection, transduction,homologous recombination, etc.) and an expression system as needed andthen the modified cells are expanded in culture and returned to thehost/patient. These genetically reimplanted cells have been shown toexpress the transfected genetic material in situ.

In in vivo gene therapy, target cells are not removed from the subjectrather the genetic material to be transferred is introduced into thecells of the recipient organism in situ, that is within the recipient.In an alternative embodiment, if the host gene is defective, the gene isrepaired in situ (Culver, 1998. (Abstract) Antisense DNA & RNA basedtherapeutics, February 1998, Coronado, Calif.).

These genetically altered cells have been shown to express thetransfected genetic material in situ.

The gene expression vehicle is capable of delivery/transfer ofheterologous nucleic acid into a host cell. The expression vehicle mayinclude elements to control targeting, expression and transcription ofthe nucleic acid in a cell selective manner as is known in the art. Itshould be noted that often the 5′UTR and/or 3′UTR of the gene may bereplaced by the 5′UTR and/or 3′UTR of the expression vehicle. Therefore,as used herein the expression vehicle may, as needed, not include the5′UTR and/or 3′UTR of the actual gene to be transferred and only includethe specific amino acid coding region.

The expression vehicle can include a promoter for controllingtranscription of the heterologous material and can be either aconstitutive or inducible promoter to allow selective transcription.Enhancers that may be required to obtain necessary transcription levelscan optionally be included. Enhancers are generally any nontranslatedDNA sequence which works contiguously with the coding sequence (in tocis) to change the basal transcription level dictated by the promoter.The expression vehicle can also include a selection gene as describedherein below.

Vectors can be introduced into cells or tissues by any one of a varietyof known methods within the art. Such methods can be found generallydescribed in Sambrook et al., Molecular Cloning: A Laboratory Manual,Cold Springs Harbor Laboratory, New York 1989, 1992), in Ausubel et al.,Current Protocols in Molecular Biology, John Wiley and Sons, Baltimore,Md. 1989), Chang et al., Somatic Gene Therapy, CRC Press, Ann Arbor,Mich. 1995), Vega et al., Gene Targeting, CRC Press, Ann Arbor Mich.(995), Vectors: A Survey of Molecular Cloning Vectors and Their Uses,Butterworths, Boston Mass. 1988) and Gilboa et al. (Biotechniques 4 (6):504-512, 1986) and include, for example, stable or transienttransfection, lipofection, electroporation and infection withrecombinant viral vectors. In addition, see U.S. Pat. No. 4,866,042 forvectors involving the central nervous system and also U.S. Pat. Nos.5,464,764 and 5,487,992 for positive-negative selection methods.

Introduction of nucleic acids by infection offers several advantagesover the other listed methods. Higher efficiency can be obtained due totheir infectious nature. Moreover, viruses are very specialized andtypically infect and propagate in specific cell types. Thus, theirnatural specificity can be used to target the vectors to specific celltypes in vivo or within a tissue or mixed culture of cells. Viralvectors can also be modified with specific receptors or ligands to altertarget specificity through receptor mediated events.

A specific example of DNA viral vector introducing and expressingrecombination sequences is the adenovirus-derived vector Adenop53TK.This vector expresses a herpes virus thymidine kinase (TK) gene foreither positive or negative selection and an expression cassette fordesired recombinant sequences. This vector can be used to infect cellsthat have an adenovirus receptor which includes most cancers ofepithelial origin as well as others. This vector as well as others thatexhibit similar desired functions can be used to treat a mixedpopulation of cells and can include, for example, an in vitro or ex vivoculture of cells, a tissue or a human subject.

Features that limit expression to particular cell types can also beincluded. Such features include, for example, promoter and regulatoryelements that are specific for the desired cell type.

In addition, recombinant viral vectors are useful for in vivo expressionof a desired nucleic acid because they offer advantages such as lateralinfection and targeting specificity. Lateral infection is inherent inthe life cycle of, for example, retrovirus and is the process by which asingle infected cell produces many progeny virions that bud off andinfect neighboring cells. The result is that a large area becomesrapidly infected, most of which was not initially infected by theoriginal viral particles. This is in contrast to vertical-type ofinfection in which the infectious agent spreads only through daughterprogeny. Viral vectors can also be produced that are unable to spreadlaterally. This characteristic can be useful if the desired purpose isto introduce a specified gene into only a localized number of targetedcells.

As described above, viruses are very specialized infectious agents thathave evolved, in may cases, to elude host defense mechanisms. Typically,viruses infect and propagate in specific cell types. The targetingspecificity of viral utilizes its natural specificity of viral vectorsutilizes its natural specificity to specifically target predeterminedcell types and thereby introduce a recombinant gene into the infectedcell. The vector to be used in the methods of the invention will dependon desired cell type to be targeted and will be known to those skilledin the art. For example, if breast cancer is to be treated then a vectorspecific for such epithelial cells would be used. Likewise, if diseasesor pathological conditions of the hematopoietic system are to betreated, then a viral vector that is specific for blood cells and theirprecursors, preferably for the specific type of hematopoietic cell,would be used.

Retroviral vectors can be constructed to function either as infectiousparticles or to undergo only a single initial round of infection. In theformer case, the genome of the virus is modified so that it maintainsall the necessary genes, regulatory sequences and packaging signals tosynthesize new viral proteins and RNA. Once these molecules aresynthesized, the host cell packages the RNA into new viral particleswhich are capable of undergoing further rounds of infection. Thevector's genome is also engineered to encode and express the desiredrecombinant gene. In the case of non-infectious viral vectors, thevector genome is usually mutated to destroy the viral packaging signalthat is required to encapsulate the RNA into viral particles. Withoutsuch a signal, any particles that are formed will not contain a genomeand therefore cannot proceed through subsequent rounds of infection. Thespecific type of vector will depend upon the intended application. Theactual vectors are also known and readily available within the art orcan be constructed by one skilled in the art using well-knownmethodology.

The recombinant vector can be administered in several ways. If viralvectors are used, for example, the procedure can take advantage of theirtarget specificity and consequently, do not have to be administeredlocally at the diseased site. However, local administration can providea quicker and more effective treatment, administration can also beperformed by, for example, intravenous or subcutaneous injection intothe subject. Injection of the viral vectors into a spinal fluid can alsobe used as a mode of administration, especially in the case ofneuro-degenerative diseases. Following injection, the viral vectors willcirculate until they recognize host cells with appropriate targetspecificity for infection.

The most common problems encountered in prior art gene therapy protocolsare poor efficacy and immune response of the host to the vector. Poorefficacy may result from failure of the delivered material to entercells, to integrate into the genome, or to be expressed at appropriatelevels. In addition, response over the course of time is often poor.This means that readministration, which might be advantageous, is oftenproblematic due to the abovementioned immune response.

Such therapeutic applications include both the enhancement, andinhibition of angiogenesis in the target tissue. Depending on thecellular response to the preferential expression of the nucleic acidsequence directed by the cis regulatory element of the presentinvention, proliferation of endothelial cells, leading to enhancedangiogenesis, or inhibition of endothelial cell proliferation, leadingto reduced angiogenesis and ischemia, can result.

Thus, inclusion of a nucleic acid sequence the expression of which iscytotoxic in the nucleic acid construct of the invention provides amethod of targeting cell death to rapidly proliferating endothelialcells in angiogenic vessels of, for example, tumors. Because such avector may be administered systemically, it can be employed toeffectively induce cell death in developing metastatic foci, in advanceof any presently available ability to identify and locate such foci ofmetastatic spread.

Such therapeutic nucleic acid sequences that can be used with theconstructs of the present invention for cancer gene therapy are oftenclassified as either corrective gene therapy, aimed at restoring mutantgene activity and control, immuno-modulatory gene therapy, aimed atsensitizing the immune system against cancer cells, and cytoreductivegene therapy, aimed at killing cancer cells by a prodrug or toxic agent(suicide gene therapy), pro-apoptotic gene, anti-angiogenic genes orenhancement of chemotherapy or radiotherapy. Nucleic acid sequencessuited for corrective gene therapy with the cis regulatory element ofthe present invention include, but are not limited to, the p53 gene(GenBank Access. No. BC018819), an anti-neoplastic, DNA-stabilizing genewhose expression is suppressed in cancer cells; Cip/Kip (p21, GenBankAcces. No. NM000389; and p27, GenBank Access. No. NM004064) and Ink4(p14, GenBank Access. No. NM058197), cyclin-dependent kinase inhibitors.Nucleic acid sequences suited for suppression of oncogene function withthe cis regulatory element of the present invention include, but are notlimited to, antisense oligonucleotides that interfere with thetranscription and translation of oncogenes such as ras, myc, erbB2 andbcl-2, and catalytic ribozymes that interfere with their translation.Methods for the synthesis and use of anti-oncogene antisense andribozyme polynucleotides are well known in the art, and are described indetail, for example, in U.S. Pat. Nos. 6,627,189 to Roth et al.,6,265,216 to Bennet et al. and 5,734,039 to Calabretta et al, all ofwhich have been incorporated fully herein by reference. Methods forpreparation and use of catalytic anti-oncogene ribozymes are described,for example, in U.S. Pat. No. 5,635,385 to Leopold et al., incorporatedfully herein by reference.

In a further embodiment of the present invention, the nucleic acidsequence expressed under control of the cis regulatory element of thepresent invention is directed to immunomodulation gene therapy, designedto prevent avoidance of immune surveillance by tumor and metastaticcells. Nucleic acid sequences encoding immunomodulatory factors suitablefor use with the cis regulatory element of the present invention arecytokine genes, intracellular molecule genes for augmenting cytotoxic Tcell recognition of Tumor Antigen and exogenous foreign immunogens (inorder to induce a non-specific local immune reaction). Suitableimmunostimulatory factors include, but are not limited to human IL-2,interferons such as human .alpha.-, .beta.- or .gamma.-interferon, humanT-cell granulocyte-macrophage colony stimulating factor (GM-CSF), humantumor necrosis factor (TNF), and lymphotoxin (TNF-b). The human IL-2gene has been cloned and sequenced and can be obtained as, for example,a 0.68 kB BamHI-HinDIII fragment from pBC12/HIV/IL-2 (available from theAmerican Type Culture Collection (“ATCC”) under Accession No. 67618).Further, the sequences of human .beta.-interferon, human GM-CSF, humanTNF and human lymphotoxin are known and are available. Particularly, thesequence of human .gamma.-interferon is known (Fiers et al. (1982)Philos. Trans. R. Soc. Lond., B, Biol. Sci. 299:29-38) and has beendeposited with GenBank under Accession No. M25460. The sequence of humanGM-CSF is known (Wong et al. (1985) Science 228:810-815) and has beendeposited with GenBank under Accession No. M10663. The sequence of humanTNF has been described (Wang et al. (1985) Science 228:149-154) and isdeposited with GenBank under Accession No. M10988. The sequence of humanlymphotoxin (TNF-b) has also been published (Iris et al. (1993) NatureGenet. 3:137-145) and is deposited with GenBank under Accession No.Z15026.

In yet a further embodiment, the nucleic acid sequence expressed undercontrol of the cis regulatory element of the present invention isdirected to cytoreductive gene therapy, or the killing of target cellsby either direct or indirect gene delivery. In one preferred embodiment,the nucleic acid sequence is a cytotoxic gene, such as, but not limitedto suicide genes such as p53 and egr-1-TNF-alpha, cytotoxicpro-drug/enzymes for drug susceptibility therapy such asganciclovir/thymidine kinase and 5-fluorocytosine/cytosine deaminase,and antimetastatic genes such as 5 E1A. Examples of specific cytotoxicconstructs are described in detail in the Examples section below.

In yet another embodiment, the nucleic acid sequence expressed undercontrol of the cis regulatory element of the present invention can bedirected to genetic radioisotopic therapy: Uptake of the radio-labeledcatecholamine I131-metaiodobenzyl-guanidine into cells which express thenoradrenaline receptor (NAT) is an established treatment modality forpheochromocytoma, neuroblastoma, carcinoid tumor and medullary thyroidcarcinoma. Alternatively, sodium iodine symporter (NIS) mediates theuptake of iodine into normal and malignant thyroid cells. The MS gene,as a transgene, has been reported to suppress prostate cancer in invitro and in vivo models.

An opposite approach may be used to re-vascularize tissue, for examplein atherosclerotic patients or in patients that have sufferedsignificant impairment of peripheral circulation as a result of diseaseor injury, such as diabetes. In this case, a construct of the typeAdPPE-1-3×-GF, where GF is a growth factor (e.g., cytokine) ormodificants thereof (e.g., AdPPE-1-SEQ ID NO:7-GF), can be employed.Suitable growth factors for use in this context include, but are notlimited to, VEGF (GenBank accession M95200) and rat PDGF-BB (GenBankaccession; 99% identity to mus-AF162784) and EGR-1 (GenBank accessionM22326) FGFs (including, but not limited to, GenBank accession XM003306) and combinations thereof.

It will be appreciated that the use of more than one angiogenic factormay be preferable according to this aspect of the present invention toavoid problems of vessel immaturity and blood vessel regression whichhave been shown to be associated with administration of VEGF alone (forfurther details see Example 27 and 31 of the Examples section). Combinedtherapy can mimic the first stage of endothelial channel sprouting andsubsequently recruitment of smooth muscle cells to stable the nascentvessels [Richardson D M et al. (2001) Nat. Biotechnol. 19:1029-1034].Combined therapy according to this aspect of the present invention maybe practiced by cloning the polynucleotides of interest on the samenucleic acid construct each of which being under the regulation of theisolated nucleic acid of the present invention. Alternatively, orpreferably, each of the polynucleotides of interest may be separatelycloned into the nucleic acid constructs of the present invention,thereby enabling a closer regulation on the induced angiogenic process.

Incorporation of a hypoxia response element (e.g. SEQ ID NO: 5) withinthe promoter sequence of the present invention can also be used with thepresent invention in order to further enhance expression selectivity toischemic tissues, thus leading to neo-vascularization of selectedtissues. As the blood supply improves, ischemia is relieved, the hypoxiaresponse element ceases to be induced, GF levels decline and theneo-vascularization process is halted.

It will be appreciated that gene therapy to endothelial tissue using thenucleic acid constructs of the present invention provides temporalcoordination unattainable with other methods unable to target angiogenicendothelial cells. As illustrated in the Examples section which follows,the cis regulatory element comprising the novel enhancer element of thepresent invention [for example, PPE-1(3×)] directs increased expressionof recombinant genes specifically in tissues undergoing vascularproliferation, while preventing recombinant gene expression in other,non-angiogenic tissues (see Examples 12, 14, 16, 19, 20, 23, 27, 29, 34and 35). Expression of therapeutic genes, under transcriptional controlof the cis regulatory elements and constructs of the present invention,coincides with the activation of the cellular processes (angiogenicgrowth processes) to which the gene products are directed, allowinggreater effectivity and significant reduction in the effective dosesrequired for treatment.

Thus, use of a construct including the cis regulatory element of thepresent invention in a gene therapy context can be expected to maximizedelivery to tumors while minimizing toxic effects on surrounding normaltissue. Significantly, this is true even if the surrounding tissuecontains an endothelial component, as illustrated in the Examplessection that follows. This is because, as demonstrated in Example 16,the cis regulatory element of the present invention greatly increasesthe level of expression in rapidly proliferating endothelial tissue,even in the context of the PPE-1 promoter.

While the examples provided hereinbelow deal specifically with the useof the cis regulatory sequence of the present invention in conjunctionwith the PPE-1 promoter, it is anticipated that the enhancer element ofthe present invention will also exert its cell specific effect when usedwith other eukaryotic promoter sequences.

Such anticipation is based on prior art findings which show thatenhancer elements are often portable, i.e., they can be transferred fromone promoter sequence to another, unrelated, promoter sequence and stillmaintain activity. For examples, see D. Jones et al. (Dev. Biol. (1995)171(1):60-72); N. S. Yew et al, (Mol. Ther. (2001) 4:75-820) and L. Wu.et al. (Gene Ther. (2001) 8; 1416-26). Indeed, the to earlier work of Buet al. (J. Biol Chem. (1997) 272(19): 32613-32622) strongly suggeststhat enhancer elements related to those of the present invention, forexample, enhancers including SEQ ID Nos. 15 and 16, or SEQ ID NO: 6 maybe used with constitutive promoters, for example the SV-40 promoter. Assuch, constructs containing, methods employing and isolatedpolynucleotides including a eukaryotic promoter modified to include theenhancer sequence of the present invention are well within the scope ofthe claimed invention.

Thus, it is postulated that a minimal configuration of an enhancerelement according to the present invention is an isolated polynucleotideincluding at least a portion of the sequence set forth in SEQ ID NO:15covalently linked to at least a portion of the sequence set forth in SEQID NO:16. This enhancer is anticipated to function with a wide varietyof promoters, including but not limited to endothelial specificpromoters (e.g. PPE-1; SEQ ID NO.: 1) and constitutive promoters, forexample viral promoters such as those derived from CMV and SV-40. Thisenhancer should be capable of imparting endothelial specificity to awide variety of promoters. The enhancer element may be augmented, forexample by addition of one or more copies of the sequence set forth inSEQ ID NO:6. These additional sequences may be added contiguously ornon-contiguously to the sequence of SEQ ID NO.: 8.

The present invention further includes a method of expressing a nucleicacid sequence of interest in endothelial cells employing a constructwhich relies upon an enhancer element including at least at least aportion of the sequence set forth in SEQ ID NO:15 covalently linked toat least a portion of the sequence set forth in SEQ ID NO:16 and apromoter to direct high level expression of the sequence of interestspecifically to endothelial cells.

As used herein “ex-vivo administration to cells removed from a body of asubject and subsequent reintroduction of the cells into the body of thesubject” specifically includes use of stem cells as described in (Lydenet al. (2001) Nature Medicine 7:1194-1201).

While adenoviruses are employed in the experiments described in examplespresented hereinbelow, the constructs of the present invention could beeasily adapted by those of ordinary skill in the art to other viraldelivery systems.

The viral vectors, containing the endothelial cell specific promoters,can also be used in combination with other approaches to enhancetargeting of the viral vectors. Such approaches include short peptideligands and/or bispecific or bifunctional molecule or diabodies(Nettelbeck et al. Molecular Therapy 3:882; 2001).

It will be noted that the host immune response to therapeutic transgenesexpressed in tissues in the context of gene therapy is a significantconcern in developing and design of effective gene therapy protocols.Adverse immune response to the recombinant transgene product can bothinterfere with the efficacy of drug delivery, and lead to inflammation,cytotoxicity, and disease. Thus, the antigenic potential of expressedrecombinant therapeutic molecules is of great importance in genetherapy.

While reducing the present invention to practice, it was unexpectedlyrevealed that a human polypeptide (TNF-R1) expressed as a portion of theAd5PPE-1(3×) nucleic acid construct (Example 41, FIG. 95 b) lacksantigenicity in mice, and does not induce a significant immunologicalresponse in the host, despite the clear anti-TNF-R1 response toadministration of the Fas-c chimera gene under control of the CMVpromoter (FIG. 95). Thus, the isolated polypeptide of the presentinvention can be used for reducing or eliminating a host immune responseto an endogenously expressed recombinant transgene product or products,effected by expressing within a cell the recombinant transgene (orgenes), under transcriptional control of the cis regulatory element ofthe present invention. Preferably, the cis regulatory element is thePPE-1 (3×) promoter.

While reducing the present invention to practice, it was suprisinglyuncovered that the angiogenic endothelial specific promoter PPE-1 (3×)is responsive to additional potentiation by anti-angiogenic therapy.FIG. 94 shows the preferential enhancement of luciferase expression inhighly vascularized organs (aorta, heart, lungs, trachea and brain) oftransgenic mice bearing a nucleic acid construct including the LUCreporter transgene under PPE-1 (3×) control, in response toadministration of the double endothelin receptor (ETA and ETB)antagonist Bosentan. This synergic effect of anti-angiogenic therapycombined with transgenic expression of a therapeutic recombinant geneunder control of the cis regulatory element of the present inventionprovides a previously undisclosed possibility for drug targeting andreduced dosage requirements for anti-angiogenic therapies. Withoutwishing to be limited by a single hypothesis, it is believed that theendogenous tissue response to antiangiogenic therapy, in activatinginducers of the endothelin promoter via an autocrine loop, in factenhance the endothelin promoter element of the nucleic acid construct ofthe present invention. Thus, in one embodiment, a construct includingthe cis regulatory element of the present invention is administered incombination with an adjunct anti-angiogenic therapy, the anti-angiogenictherapy selected capable of inducing an endogenous enhancer ofendothelial-specific promoter activity. Anti-angiogenic therapy wellknown in the art includes, but is not limited to endothelin receptorantagonists such as Bosentan, VEGF-receptor antagonists, angiostatin andendostatin, and antiangiogenic antibodies such as Bevacizumab andNovast.

The constructs and methods of the present invention are especiallysuited for use in tissue engineering. VEGF and PDGF are commonly used toinduce vascularization, however methods of administration of thesefactors in an effective way are still not optimal. In vitro, the growthfactors are added in the growth medium. In this method relatively highconcentration are needed. In vivo, engineered tissue constructs need tobe vascularized rapidly and to induce angiogenesis to the site ofimplantation. The cis regulatory elements and nucleic acid constructs ofthe present invention can be used for neovascularization of tissue invivo and ex-vivo, for example, for use in tissue engineering, treatmentof wound healing, and the like. While reducing the present invention topractice, it was demonstrated, for the first time, that angiogenicfactors, under regulatory control of PPE-1(3×), are preferentiallyexpressed in vascularized in-vitro engineered tissue and providesuperior neovascularization in engineered tissue in-vitro and in-vivo.

Infection of the cells with Ad5PPEC-1-3×VEGF has an inductive effect onnumber and size of vessels-like structures formed in the engineeredconstructs, resulting in a 4-5 fold increase in the number of vesselsand percentages of vessel area in the samples treated withAd5PPEC-1-3×VEGF virus comparing to addition of VEGF to the medium (FIG.91 a). In in-vivo studies. survival, differentiation, integration andvascularization of implanted scaffold-based tissue constructs wereanalyzed. Constructs infected with Ad5PPEC-1-3×VEGF virus show anincrease in vessel structures compared to control constructs.

Thus in one preferred embodiment, the nucleic acid construct of thepresent invention is used to regulate angiogenesis in a tissue, thetissue being a natural or an engineered tissue.

Employing a luciferase-based imaging system, the present inventorsuncovered that implanted constructs infected with Ad5PPEC-1-3×VEGF hadhigher signal than control constructs infected with AAV-luciferase only,indicating that in vitro infection with Ad5PPEC-1-3×VEGF can improvesurvival and vascularization of implanted engineered tissue constructs(FIG. 91 b). Further, such engineered tissue constructs comprising cellstransduced with adenovirus constructs of the present invention canconstitute a source of therapeutic, recombinant virus particles forsurrounding tissue via cell lysis.

Thus, according to one aspect of the present invention, there isprovided a cell comprising the nucleic acid construct of the presentinvention. According to yet another aspect of the present invention,these cells are used to seed a scaffold to be used, for example, fortissue engineering. Methods for tissue engineering using scaffolds arewell known in the art (see, for example, U.S. Pat. Nos. 6,753,181;6,652,583; 6,497,725; 6,479,064; 6,438,802; 6,376,244; 6,206,917,6,783,776; 6,576,265; 6,521,750; 6,444,803; 6,300,127; 6,183,737;6,110,480; 6,027,743; and 5,906,827, and US Patent Application Nos.0040044403; 0030215945; 0030194802; 0030180268; 0030124099; 0020160510;0020102727, incorporated herein by reference, all of which teachgeneration of engineered tissue on tissue scaffolds). Suitable scaffoldscan be composed of synthetic polymer, a cell adhesion molecule or anextracellular matrix protein.

The cell adhesion/ECM protein used by the present invention can be anycell adhesion and/or extracellular matrix protein, including, but notlimited to, fibrinogen, Collagen, integrin (Stefanidakis M, et al.,2003; J Biol Chem. 278: 34674-84), intercellular adhesion molecule(ICAM) 1 (van de Stolpe A and van der Saag P T. 1996; J. Mol. Med. 74:13-33), tenascin, fibrinectin (Joshi P, et al., 1993; J. Cell Sci. 106:389-400); vimentin, microtubule-associated protein 1D (Theodosis D T.2002; Front Neuroendocrinol. 23: 101-35), gicerin, Neurite outgrowthfactor (NOF) (Tsukamoto Y, et al., 2001; Histol. Histopathol. 16:563-71), polyhydroxyalkanoate (PHA), bacterial cellulose (BC), gelatin,and/or nerve injury induced protein 2 (ninjurin2) (Araki T and MilbrandtJ. 2000; J. Neurosci. 20: 187-95).

The synthetic polymer used by the present invention can be polyethyleneglycol (PEG), Hydroxyapatite (HA), polyglycolic acid (PGA) (Freed L E,Biotechnology (N Y). 1994 July; 12(7):689-93), epsilon-caprolactone and1-lactic acid reinforced with a poly-1-lactide knitted [KN-PCLA] (OzawaT et al., 2002; J. Thorac. Cardiovasc. Surg. 124: 1157-64), woven fabric(WV-PCLA) [Ozawa, 2002 (Supra)], interconnected-porous calciumhydroxyapatite ceramics (IP-CHA), poly D,L-lacticacid-polyethyleneglycol (PLA-PEG) (Kaito T et al., 2005; Biomaterials.26: 73-9), unsaturated polyester poly(propylene glycol-co-fumaric acid)(PPF) (Trantolo D J et al., 2003; Int. J. Oral Maxillofac. Implants. 18:182-8), polylactide-co-glycolide (PLAGA) (Lu H H, et al., 2003; J.Biomed. Mater. Res. 64A(3): 465-74), poly-4-hydroxybutyrate (P4HB),and/or polyphosphazene (Cohen S et al., 1993; Clin. Mater. 13(1-4):3-10).

While reducing the present invention to practice, the present inventorshave uncovered that a combination of tissue-specific expression andspecific activation of a pro-apoptotic agent enables selective apoptosisof cells involved in angiogenesis without exposing non-targeted tissueor cells to these agents, thus, avoiding the toxic side effects andredundancy characterizing prior art treatment approaches.

Thus, according to one aspect of the present invention there is provideda method of down-regulating angiogenesis in a tissue of a subject. Asused herein, the phrase “down-regulating angiogenesis” refers to eitherslowing down or stopping the angiogenic process, which lead to formationof new blood vessels.

The method according to this aspect of the present invention is effectedby administering to the subject a nucleic acid construct designed andconfigured for cytotoxicity in a sub-population of angiogenic cells. Asused herein, the phrase “angiogenic cells” refers to any cells, whichparticipate or contribute to the process of angiogenesis. Thus,angiogenic cells include but are not limited to, endothelial cells,smooth muscle cells.

As use herein, the term “cytotoxicity” refers to the ability of acompound or to process to disrupt the normal metabolism, function and/orstructure of a cell, in a potentially irreversible manner, most oftenleading to cell death. A “cytotoxic molecule” is herein defined as amolecule having, under defined conditions, the capability of generatingcytotoxicity, or inducing a cytotoxic process or pathway within a cell.Such cytotoxic molecules include cytotoxic drugs such as, but notlimited to antimetabolites such as methotrexate, nucleoside analogues,nitrogen mustard compounds, anthracyclines, inducers of apoptosis suchas caspase, as well as genes encoding cytotoxic drugs and other inducersof cytotoxic processes, such as the Fas-c chimera gene. Cytotoxic drugsand molecules may be absolutely cytotoxic, independent of other factors,such as antimetabolite drugs, or conditionally cytotoxic, dependent onthe interplay of other, cytotoxic or non-cytotoxic factors. A cytotoxicgenerating domain is defined as a portion of a cytotoxic moleculecapable of inducing or initiating cytotoxicity, such as a codingsequence of a cytotoxic gene. Cytotoxic pathways include, inter alia,apoptosis and necrosis.

In one preferred embodiment of the present invention, the expression ofthe cytotoxic agent is directed to a subpopulation of angiogenic cells.In order to direct specific expression of a cytotoxic agent in asubpopulation of angiogenic cells, the nucleic acid construct of thepresent invention includes a first polynucleotide region encoding achimeric polypeptide including a ligand binding domain which can be, forexample, a cell-surface receptor domain of a receptor tyrosine kinase, areceptor serine kinase, a receptor threonine kinase, a cell adhesionmolecule or a phosphatase receptor fused to an effector domain of ancytotoxic molecule such as, for example, Fas, TNFR, and TRAIL.

Such a chimeric polypeptide can include any ligand binding domain fusedto any cytotoxic domain as long as activation of the ligand bindingdomain, i.e., via ligand binding, triggers cytotoxicity via the effectordomain of the cytotoxic molecule.

Selection of the ligand binding domain and the cytotoxicity generatingdomain fused thereto is affected according to the type of angiogeniccell targeted for apoptosis. For example, when targeting specific subsetof endothelial cells (e.g., proliferating endothelial cells, orendothelial cells exhibiting a tumorous phenotype), the chimericpolypeptide includes a ligand binding domain capable of binding a ligandnaturally present in the environment of such endothelial cells andpreferably not to present in endothelial cells of other non-targetedtissues (e.g., TNF, VEGF). Such a ligand can be secreted by endothelialcells (autocrine), secreted by neighboring tumor cells (paracrine) orspecifically targeted to these endothelial cells.

Examples of suitable chimeric polypeptides are provided hereinabove, andin Examples 7 and 33-36 of the Examples section which follows.Preferably, the chimeric polypeptide is the Fas-c chimera which isdescribed in detail in Examples 7-9 of the Examples section whichfollows, or the HSV-TK gene described in Examples 33-36. Expression ofthe Fas-c chimera has been shown to induce apoptosis via FADD-mediatedactivation of the Fas death pathway. Expression of the HSV-TK transgeneresults in hypersusceptibility of the transduced cells to drugs such asganciclovir and aciclovir, leading to apoptosis and necrotic cell death.

The use of such a chimeric polypeptide is particularly advantageous,since, as shown in the Examples section hereinunder, it enablesefficient and robust activation of cytotoxicity in a specific subset ofangiogenic cells while avoiding activation in other subset of cells,which are not targeted for cell death.

As is illustrated in Examples 33-38 that of the Examples section thatfollow, both in-vitro and in-vivo administration of nucleic acidconstructs of the present invention, including the HSV-TK gene undertranscriptional control of the PPE-1 (3×) promoter element, producedsuperior, ganciclovir-dependent endothelial cell cytotoxicity.Cytotoxicity was restricted to angiogenic endothelial cells, producingselective apoptotic and necrotic cell death in tumors and metastases.

Thus, the nucleic acid construct of the present invention can be used todeliver a suicide gene, capable of converting a prodrug to a toxiccompound. In one preferred embodiment the nucleic acid constructincludes a first polynucleotide region encoding such a suicide gene, anda second polynucleotide region encoding a cis acting regulatory elementcapable of directing expression of the suicide gene in angiogenic cells.

In the constructs and methods of the present invention, the therapeuticnucleic acid sequence or “suicide gene” is a nucleic acid coding for aproduct, wherein the product causes cell death by itself or in thepresence of other compounds. It will be appreciated that the abovedescribed construct represents only one example of a suicide construct.Additional examples are thymidine kinase of varicella zoster virus andthe bacterial gene cytosine deaminase which can convert 5-fluorocytosineto the highly toxic compound 5-fluorouracil.

As used herein “prodrug” means any compound useful in the methods of thepresent invention that can be converted to a toxic product, i.e. toxicto tumor cells. The prodrug is converted to a toxic product by the geneproduct of the therapeutic nucleic acid sequence (suicide gene) in thevector useful in the method of the present invention. Representativeexamples of such a prodrug is ganciclovir which is converted in vivo toa toxic compound by HSV-thymidine kinase. The ganciclovir derivativesubsequently is toxic to tumor cells. Other representative examples ofprodrugs include aciclovir, FIAU[1-(2-deoxy-2-fluoro-.beta.-D-arabinofuranosyl)-5-iodourdcil],6-methoxypurine arabinoside for VZV-TK, and 5-fluorocytosine forcytosine deambinase. Preferred suicide gene/prodrug combinations arebacteria cytosine deaminase and 5-fluorocytosine and its derivatives,varicella zoster virus TK and 6-methylpurine arabinoside and itsderivatives, HSV-TK and ganciclovir, aciclovir, FIAU or theirderivatives. Methods for preparation and use of suicide gene/prodrugconstructs are described in detail in U.S. Pat. No. 6,066,624 to Woo etal., and in the Examples section which follows.

In one preferred embodiment, the cis acting regulatory element is anendothelial or periendothelial specific promoter. Since transduction ofcells with conditionally replicating adenoviral vectors is significantlymore effective in target cell lysis and spread of viral infection, thenucleic acid construct can preferably include a conditionallyreplicating adenovirus. Such CRAD constructs of the present inventionare described in detail in the Examples section here which follows.

Preferably, the nucleic acid construct of the present invention isadministered to the subject via, for example, systemic administrationroutes or via oral, rectal, transmucosal (especially transnasal),intestinal or parenteral administration routes. Systemic administrationincludes intramuscular, subcutaneous and intramedullary injections aswell as intrathecal, direct intraventricular, intravenous,intraperitoneal, intranasal, intraocular injections or intra-tumoral.

Preferably, the subject is a mammal, more preferably, a human being,most preferably, a human being suffering from diseases characterized byexcessive or abnormal neovascularization such as that characterizingtumor growth, proliferating diabetic retinopathy, arthritis and thelike.

The nucleic acid constructs of the present invention can be administeredto the subject per se or as part (active ingredient) of a pharmaceuticalcomposition.

The prior art teaches of a number of delivery strategies which can beused to efficiently deliver naked or carrier provided polynucleotidesinto a wide variety of cell types (see, for example, Luft (1998) J MolMed 76(2): 75-6; Kronenwett et al. (1998) Blood 91(3): 852-62; Rajur etal. (1997) Bioconjug Chem 8(6): 935-40; Lavigne et al. (1997) BiochemBiophys Res Commun 237(3): 566-71 and Aoki et al. (1997) Biochem BiophysRes Commun 231(3): 540-5).

As used herein a “pharmaceutical composition” refers to a preparation ofone or more of the active ingredients or agents described herein withother chemical components such as physiologically suitable carriers andexcipients. The purpose of a pharmaceutical composition is to facilitateadministration of a compound to an organism.

Hereinafter, the phrases “physiologically acceptable carrier” and“pharmaceutically acceptable carrier” which may be interchangeably usedrefer to a carrier or a diluent that does not cause significantirritation to an organism and does not abrogate the biological activityand properties of the administered nucleic acid construct. An adjuvantis included under these phrases.

Herein the term “excipient” refers to an inert substance added to apharmaceutical composition to further facilitate administration of anactive ingredient. Examples, without limitation, of excipients includecalcium carbonate, calcium phosphate, various sugars and types ofstarch, cellulose derivatives, gelatin, vegetable oils and polyethyleneglycols.

Techniques for formulation and administration of drugs may be found in“Remington's Pharmaceutical Sciences,” Mack Publishing Co., Easton, Pa.,latest edition, which is incorporated herein by reference.

Suitable routes of administration may, for example, include oral,rectal, transmucosal, especially transnasal, intestinal or parenteraldelivery, including intramuscular, subcutaneous and intramedullaryinjections as well as intrathecal, direct intraventricular, intravenous,intraperitoneal, intranasal, or intraocular injections.

Alternately, one may administer the pharmaceutical composition in alocal rather than systemic manner, for example, via injection of thepharmaceutical composition directly into a tissue region of a patient.In the context of the present invention, administration directly intotumor tissue is a relevant example of local administration.

Pharmaceutical compositions of the present invention may be manufacturedby processes well known in the art, e.g., by means of conventionalmixing, dissolving, granulating, dragee-making, levigating, emulsifying,encapsulating, entrapping or lyophilizing processes.

Pharmaceutical compositions for use in accordance with the presentinvention thus may be formulated in conventional manner using one ormore physiologically acceptable carriers comprising excipients andauxiliaries, which facilitate processing of the active ingredients intopreparations which can be used pharmaceutically. Proper formulation isdependent upon the route of administration chosen.

For injection, the active ingredient of the pharmaceutical compositionmay be formulated in aqueous solutions, preferably in physiologicallycompatible buffers such as Hank's solution, Ringer's solution, orphysiological salt buffer. For transmucosal administration, penetrantsappropriate to the barrier to be permeated are used in the formulation.Such penetrants are generally known in the art.

For oral administration, the pharmaceutical composition can beformulated readily by combining the active compounds withpharmaceutically acceptable carriers well known in the art. Suchcarriers enable the pharmaceutical composition to be formulated astablets, pills, dragees, capsules, liquids, gels, syrups, slurries,suspensions, and the like, for oral ingestion by a patient.Pharmacological preparations for oral use can be made using a solidexcipient, optionally grinding the resulting mixture, and processing themixture of granules, after adding suitable auxiliaries if desired, toobtain tablets or dragee cores. Suitable excipients are, in particular,fillers such as sugars, including lactose, sucrose, mannitol, orsorbitol; cellulose preparations such as, for example, maize starch,wheat starch, rice starch, potato starch, gelatin, gum tragacanth,methyl cellulose, hydroxypropylmethyl-cellulose, sodiumcarbomethylcellulose; and/or physiologically acceptable polymers to suchas polyvinylpyrrolidone (PVP). If desired, disintegrating agents may beadded, such as cross-linked polyvinyl pyrrolidone, agar, or alginic acidor a salt thereof such as sodium alginate.

Dragee cores are provided with suitable coatings. For this purpose,concentrated sugar solutions may be used which may optionally containgum arabic, talc, polyvinyl pyrrolidone, carbopol gel, polyethyleneglycol, titanium dioxide, lacquer solutions and suitable organicsolvents or solvent mixtures. Dyestuffs or pigments may be added to thetablets or dragee coatings for identification or to characterizedifferent combinations of active compound doses.

Pharmaceutical compositions which can be used orally, include push-fitcapsules made of gelatin as well as soft, sealed capsules made ofgelatin and a plasticizer, such as glycerol or sorbitol. The push-fitcapsules may contain the active ingredients in admixture with fillersuch as lactose, binders such as starches, lubricants such as talc ormagnesium stearate and, optionally, stabilizers. In soft capsules, theactive ingredients may be dissolved or suspended in suitable liquids,such as fatty oils, liquid paraffin, or liquid polyethylene glycols. Inaddition, stabilizers may be added. All formulations for oraladministration should be in dosages suitable for the chosen route ofadministration.

For buccal administration, the compositions may take the form of tabletsor lozenges formulated in conventional manner.

For administration by nasal inhalation, the active ingredients for useaccording to the present invention are conveniently delivered in theform of an aerosol spray presentation from a pressurized pack or anebulizer with the use of a suitable propellant, e.g.,dichlorodifluoromethane, trichlorofluoromethane,dichlorotetrafluoroethane or carbon dioxide. In the case of apressurized aerosol, the dosage unit may be determined by providing avalve to deliver a metered amount. Capsules and cartridges of, e.g.,gelatin for use in a dispenser may be formulated containing a powder mixof the compound and a suitable powder base such as lactose or starch.

The pharmaceutical composition described herein may be formulated forparenteral administration, e.g., by bolus injection or continuousinfusion. Formulations for injection may be presented in unit dosageform, e.g., in ampoules or in multidose containers with optionally, anadded preservative. The compositions may be suspensions, solutions oremulsions in oily or aqueous vehicles, and may contain formulatoryagents such as suspending, stabilizing and/or dispersing agents.

Pharmaceutical compositions for parenteral administration includeaqueous solutions of the active preparation in water-soluble form.Additionally, suspensions of the active ingredients may be prepared asappropriate oily or water based injection is suspensions. Suitablelipophilic solvents or vehicles include fatty oils such as sesame oil,or synthetic fatty acids esters such as ethyl oleate, triglycerides orliposomes. Aqueous injection suspensions may contain substances, whichincrease the viscosity of the suspension, such as sodium carboxymethylcellulose, sorbitol or dextran. Optionally, the suspension may alsocontain suitable stabilizers or agents which increase the solubility ofthe active ingredients to allow for the preparation of highlyconcentrated solutions.

Alternatively, the active ingredient may be in powder form forconstitution with a suitable vehicle, e.g., sterile, pyrogen-free waterbased solution, before use.

The pharmaceutical composition of the present invention may also beformulated in rectal compositions such as suppositories or retentionenemas, using, e.g., conventional suppository bases such as cocoa butteror other glycerides.

Pharmaceutical compositions suitable for use in context of the presentinvention include compositions wherein the active ingredients arecontained in an amount effective to achieve the intended purpose. Morespecifically, a therapeutically effective amount means an amount ofactive ingredients (e.g. antisense oligonucleotide) effective toprevent, alleviate or ameliorate symptoms of a disorder (e.g.,progressive loss of bone mass) or prolong the survival of the subjectbeing treated.

Determination of a therapeutically effective amount is well within thecapability of those skilled in the art, especially in light of thedetailed disclosure provided herein.

For any preparation used in the methods of the invention, thetherapeutically effective amount or dose can be estimated initially fromin vitro and cell culture assays. For example, a dose can be formulatedin an animal model, such as the murine Src deficient model ofosteopetrosis (Boyce et al. (1992) J. Clin. Invest. 90, 1622-1627; Loweet al. (1993) Proc. Natl. Acad. Sci. USA 90, 4485-4489; Soriano et al.(1991) Cell 64, 693-702), to achieve a desired concentration or titer.Such information can be used to more accurately determine useful dosesin humans.

Toxicity, cytotoxicity and therapeutic efficacy of the activeingredients described herein can be determined by standardpharmaceutical procedures in vitro, in cell cultures or experimentalanimals. The data obtained from these in vitro and cell culture assaysand animal studies can be used in formulating a range of dosage for usein human. The dosage may vary depending upon the dosage form employedand the route of administration utilized. The exact formulation, routeof administration and dosage can be chosen by the individual physicianin view of the patient's condition. (See e.g., Fingl, et al., 1975, in“The Pharmacological Basis of Therapeutics”, Ch. 1 p. 1).

Dosage amount and interval may be adjusted individually to levels of theactive ingredient are sufficient to retard tumor progression (minimaleffective concentration, MEC). The MEC will vary for each preparation,but can be estimated from in vitro data. Dosages necessary to achievethe MEC will depend on individual characteristics and route ofadministration. Detection assays can be used to determine plasmaconcentrations.

Depending on the severity and responsiveness of the condition to betreated, dosing can be of a single or a plurality of administrations,with course of treatment lasting from several days to several weeks ordiminution of the disease state is achieved.

The amount of a composition to be administered will, of course, bedependent on the subject being treated, the severity of the affliction,the manner of administration, the judgment of the prescribing physician,etc.

Compositions of the present invention may, if desired, be presented in apack or dispenser device, such as an FDA approved kit, which may containone or more unit dosage forms containing the active ingredient. The packmay, for example, comprise metal or plastic foil, such as a blisterpack. The pack or dispenser device may be accompanied by instructionsfor administration. The pack or dispenser may also be accommodated by anotice associated with the container in a form prescribed by agovernmental agency regulating the manufacture, use or sale ofpharmaceuticals, which notice is reflective of approval by the agency ofthe form of the compositions or human or veterinary administration. Suchnotice, for example, may be of labeling approved by the U.S. Food andDrug Administration for prescription drugs or of an approved productinsert. Compositions comprising a preparation of the inventionformulated in a compatible pharmaceutical carrier may also be prepared,placed in an appropriate container, and labeled for treatment of anindicated condition, as if further detailed above.

The pharmaceutical compositions of the present invention may furtherinclude any additional ingredients which may improve the uptake of thenucleic acid construct by the cells, expression of the chimericpolypeptide or suicide gene encoded by the nucleic acid construct in thecells, or the activity of the expressed chimeric polypeptide or suicidegene product.

For example, the uptake of adenoviral vectors into EC cells can beenhanced by treating the vectors with engineered antibodies or smallpeptides. Such “adenobody” treatment, was shown effective in directingadenovirus constructs to EGF receptors on cells (Watkins et al 1997,Gene Therapy 4:1004-1012). In addition, Nicklin et al have shown that asmall peptide, isolated via phage display, increased specificity andefficiency of vectors in endothelial cells and decreased the expressionin liver cells in culture (Nicklin et al 2000, Circulation 102:231-237).In a recent study, an FGF retargeted adenoviral vector reduced thetoxicity of tk in mice (Printz et al 2000, Human Gene Therapy11:191-204).

Low dose radiation has been shown to cause breaks in DNA strandsprimarily in the G2/M phase, cell membrane damage enhancing thebystander effect, and thus may potentiate other cytotoxic andanti-neoplastic therapies, when administered in combination. Vascularendothelial cells may be particularly suitable to such combination, oradjunct, therapies, since it has been demonstrated that low doseradiation specifically targets the apoptotic system of the microvascularendothelial cells (Kolesnick et al., Oncogene 2003; 22:5897-906).Angiostatin has been shown to potentiate the therapeutic effects of lowdose radiation (Gorski et al. Can Res 1998; 58:5686-89). However, theeffects of radiation are still poorly understood, since irradiation hasalso been shown to increase pro-angiogenic “tissue repair factors”(Itasaka et al., Am Assoc Canc Res, 2003; abstract 115). Similarly,certain chemotherapeutic agents have been shown to activate specificcytotoxic and apoptotic pathways [doxorubicin, cisplatin and mitomycin Cinduce accumulation of Fas receptor, FADD, and other proapoptoticsignals in the FADD/MORT-1 pathway (Micheau et al., BBRC 1999256:603-07)]. While reducing the present invention to practice, it wassurprisingly uncovered that low dose radiation treatment has a clearsynergistic effect on the anti-tumor and anti metastatic effectivenessof nucleic acid constructs including TK under control of PPE-1(3×) andganciclovir administration (Examples 35 and 36 FIGS. 79-86). This is ofspecific relevance in the context of the present invention, since it hasbeen demonstrated that such low dose radiation can activate TKexpression and therapeutic effect, can specifically potentiatedoxorubicin chemotherapeutic effect, and is known to activate theFADD/MORT-1 apoptotic pathway (Kim et al, JBC 2002; 277:38855-62).

Further evidence of the efficacy of such combination therapy isdescribed in Example 37, which illustrates the synergic effect ofcombined doxorubicin and AdPPE-1 (3×)-Fas-c chimera constructadministration in endothelial cells (BAEC) (FIG. 91). Thus, nucleic acidconstructs and the pharmaceutical compositions comprising same of thepresent invention can be used to treat diseases or conditions associatedwith aberrant angiogenesis alone or in combination with one or moreother established or experimental therapeutic regimen for suchdisorders. Therapeutic regimen for treatment of cancer suitable forcombination with the nucleic acid constructs of the present invention orpolynucleotide encoding same include, but are not limited tochemotherapy, radiotherapy, phototherapy and photodynamic therapy,surgery, nutritional therapy, ablative therapy, combined radiotherapyand chemotherapy, brachiotherapy, proton beam therapy, immunotherapy,cellular therapy and photon beam radiosurgical therapy.

Anti-cancer drugs that can be co-administered with the compounds of theinvention include, but are not limited to Acivicin; Aclarubicin;Acodazole Hydrochloride; Acronine; Adriamycin; Adozelesin; Aldesleukin;Altretamine; Ambomycin; Ametantrone Acetate; Aminoglutethimide;Amsacrine; Anastrozole; Anthramycin; Asparaginase; Asperlin;Azacitidine; Azetepa; Azotomycin; Batimastat; Benzodepa; Bicalutamide;Bisantrene Hydrochloride; Bisnafide Dimesylate; Bizelesin; BleomycinSulfate; Brequinar Sodium; Bropirimine; Busulfan; Cactinomycin;Calusterone; Caracemide; Carbetimer; Carboplatin; Carmustine; CarubicinHydrochloride; Carzelesin; Cedefingol; Chlorambucil; Cirolemycin;Cisplatin; Cladribine; Crisnatol Mesylate; Cyclophosphamide; Cytarabine;Dacarbazine; Dactinomycin; Daunorubicin Hydrochloride; Decitabine;Dexormaplatin; Dezaguanine; Dezaguanine Mesylate; Diaziquone; Docetaxel;Doxorubicin; Doxorubicin Hydrochloride; Droloxifene; DroloxifeneCitrate; Dromostanolone Propionate; Duazomycin; Edatrexate; EflornithineHydrochloride; Elsamitrucin; Enloplatin; Enpromate; Epipropidine;Epirubicin Hydrochloride; Erbulozole; Esorubicin Hydrochloride;Estramustine; Estramustine Phosphate Sodium; Etanidazole; Etoposide;Etoposide Phosphate; Etoprine; Fadrozole Hydrochloride; Fazarabine;Fenretinide; Floxuridine; Fludarabine Phosphate; Fluorouracil;Fluorocitabine; Fosquidone; Fostriecin Sodium; Gemcitabine; GemcitabineHydrochloride; Hydroxyurea; Idarubicin Hydrochloride; Ifosfamide;Ilmofosine; Interferon Alfa-2a; Interferon Alfa-2b; Interferon Alfa-n1;Interferon Alfa-n3; Interferon Beta-I a; Interferon Gamma-I b;Iproplatin; Irinotecan Hydrochloride; Lanreotide Acetate; Letrozole;Leuprolide Acetate; Liarozole Hydrochloride; Lometrexol Sodium;Lomustine; Losoxantrone Hydrochloride; Masoprocol; Maytansine;Mechlorethamine Hydrochloride; Megestrol Acetate; Melengestrol Acetate;Melphalan; Menogaril; Mercaptopurine; Methotrexate; Methotrexate Sodium;Metoprine; Meturedepa; Mitindomide; Mitocarcin; Mitocromin; Mitogillin;Mitomalcin; Mitomycin; Mitosper; Mitotane; Mitoxantrone Hydrochloride;Mycophenolic Acid; Nocodazole; Nogalamycin; Ormaplatin; Oxisuran;Paclitaxel; Pegaspargase; Peliomycin; Pentamustine; Peplomycin Sulfate;Perfosfamide; Pipobroman; Piposulfan; Piroxantrone Hydrochloride;Plicamycin; Plomestane; Porfimer Sodium; Porfiromycin; Prednimustine;Procarbazine Hydrochloride; Puromycin; Puromycin Hydrochloride;Pyrazofurin; Riboprine; Rogletimide; Safingol; Safingol Hydrochloride;Semustine; Simtrazene; Sparfosate Sodium; Sparsomycin; SpirogermaniumHydrochloride; Spiromustine; Spiroplatin; Streptonigrin; Streptozocin;Sulofenur; Talisomycin; Taxol; Tecogalan Sodium; Tegafur; TeloxantroneHydrochloride; Temoporfin; Teniposide; Teroxirone; Testolactone;Thiamiprine; Thioguanine; Thiotepa; Tiazofuirin; Tirapazamine; TopotecanHydrochloride; Toremifene Citrate; Trestolone Acetate; TriciribinePhosphate; Trimetrexate; Trimetrexate Glucuronate; Triptorelin;Tubulozole Hydrochloride; Uracil Mustard; Uredepa; Vapreotide;Verteporfin; Vinblastine Sulfate; Vincristine Sulfate; Vindesine;Vindesine Sulfate; Vinepidine Sulfate; Vinglycinate Sulfate;Vinleurosine Sulfate; Vinorelbine Tartrate; Vinrosidine Sulfate;Vinzolidine Sulfate; Vorozole; Zeniplatin; Zinostatin; ZorubicinHydrochloride. Additional antineoplastic agents include those disclosedin Chapter 52, Antineoplastic Agents (Paul Calabresi and Bruce A.Chabner), and the introduction thereto, 1202-1263, of Goodman andGilman's “The Pharmacological Basis of Therapeutics”, Eighth Edition,1990, McGraw-Hill, Inc. (Health Professions Division).

It will be appreciated that although targeting of cells exposed to theligand, or to the cytotoxic prodrug is preferred, the present inventionalso envisages expression of the nucleic acid construct of the presentinvention in cells which are not exposed to, or naturally affected bythe ligand or cytotoxic prodrug. In such cases, the method of thepresent invention includes the step of administering such a ligand, orprodrug, to the cells transformed. Such administration can be effectedby using any of the above described administration methods. Preferably,the ligand or prodrug is administrated in a cell targeted manner, usingfor example antibody conjugated targeting, such that activation ofcytotoxicity is highly specific. This approach of cytotoxic or apoptoticactivation is described in more detail in the Examples section whichfollows.

Thus, the present invention provides nucleic acid constructs,pharmaceutical compositions including such constructs and methods ofutilizing such constructs for down-regulating angiogenesis in tissueregions characterized by excessive or abnormal angiogenesis.

Since the present invention enables targeted expression in specific cellsubsets, it can also be modified and used in for treating varioustumors.

Thus, according to another aspect of the present invention there isprovided a method of treating tumors.

The method according to this aspect of the present invention is effectedby expressing in tumor cells the chimeric polypeptide or suicide genedescribed above.

Thus according to this aspect of the present invention, expression ofthe polypeptide chimera or suicide gene is directed by a tumor specificelement, such as, but not limited to, the gastrin-releasing peptide(GRP) promoter [AF293321S3; Morimoto E Anticancer Res 2001January-February; 21(1A):329-31], the hTERT promoter [AH007699; Gu J,Gene Ther 2002 January; 9(1):30-7], the Hexokinase type II promoter[AF148512; Katabi M M, Hum Gene Ther. 1999 Jan. 20; 10(2):155-64.], orthe L-plastin promoter [L05490, AH002870, MMU82611; Peng X Y, CancerRes. 2001 Jun. 1; 61(10:4405-13].

Expression of the polypeptide chimera (e.g., Fas-c) or suicide gene intumor cells activates cytotoxicity and/or apoptosis in these cells andthus leads to cell death, which in turn causes tumor growth slowdown orarrest, and possibly tumor shrinkage.

Additional objects, advantages, and novel features of the presentinvention will become apparent to one ordinarily skilled in the art uponexamination of the following examples, which are not intended to belimiting. Additionally, each of the various embodiments and aspects ofthe present invention as delineated hereinabove and as claimed in theclaims section below finds experimental support in the followingexamples.

EXAMPLES

Reference is now made to the following examples, which together with theabove descriptions, illustrate the invention in a non-limiting fashion.

Generally, the nomenclature used herein and the laboratory proceduresutilized in the present invention include molecular, biochemical,microbiological and recombinant DNA techniques. Such techniques arethoroughly explained in the literature. See, for example, “MolecularCloning: A laboratory Manual” Sambrook et al., (1989); “CurrentProtocols in Molecular Biology” Volumes I-III Ausubel, R. M., ed.(1994); Ausubel et al., “Current Protocols in Molecular Biology”, JohnWiley and Sons, Baltimore, Md. (1989); Perbal, “A Practical Guide toMolecular Cloning”, John Wiley & Sons, New York (1988); Watson et al.,“Recombinant DNA”, Scientific American Books, New York; Birren et al.(eds) “Genome Analysis: A Laboratory Manual Series”, Vols. 1-4, ColdSpring Harbor Laboratory Press, New York (1998); methodologies set forthin U.S. Pat. Nos. 4,666,828; 4,683,202; 4,801,531; 5,192,659 and5,272,057; “Cell Biology: A Laboratory Handbook”, Volumes I-III Cellis,J. E., ed. (1994); “Current Protocols in Immunology” Volumes Coligan J.E., ed. (1994); Stites et al. (eds), “Basic and Clinical immunology”(8th Edition), Appleton & Lange, Norwalk, Conn. (1994); Mishell andShiigi (eds), “Selected Methods in Cellular Immunology”, W. H. Freemanand Co., New York (1980); available immunoassays are extensivelydescribed in the patent and scientific literature, see, for example,U.S. Pat. Nos. 3,791,932; 3,839,153; 3,850,752; 3,850,578; 3,853,987;3,867,517; 3,879,262; 3,901,654; 3,935,074; 3,984,533; 3,996,345;4,034,074; 4,098,876; 4,879,219; 5,011,771 and 5,281,521;“Oligonucleotide Synthesis” Gait, M. J., ed. (1984); “Nucleic AcidHybridization” Hames, B. D., and Higgins S. J., eds. (1985);“Transcription and Translation” flames, B. D., and Higgins S. J., eds.(1984); “Animal Cell Culture” Freshney, R. I., ed. (1986); “ImmobilizedCells and Enzymes” IRL Press, (1986); “A Practical Guide to MolecularCloning” Perbal, B., (1984) and “Methods in Enzymology” Vol. 1-317,Academic Press; “PCR Protocols: A Guide To Methods And Applications”,Academic Press, San Diego, Calif. (1990); Marshak et al., “Strategiesfor Protein Purification and Characterization—A Laboratory CourseManual” CSHL Press (1996); all of which are incorporated by reference asif fully set forth herein. Other general references are providedthroughout this document. The procedures therein are believed to be wellknown in the art and are provided for the convenience of the reader. Allthe information contained therein is incorporated herein by reference.

Specifically, experiments conducted in conjunction with the examplesrecited hereinbelow employed the following methods and materials:

Materials and Methods

Cell Culture

Lewis Lung Carcinoma—(D122-96), Human Embryonic Kidney (293) and HeLacells were grown in 4.5 gr/l DMEM, supplemented with 10% fetal calfserum (FCS), 50 U/ml penicillin, 50 μg/ml streptomycin and 2 mMglutamine (Biological industries, Beit-Haemek, Israel). Bovine AorticEndothelial Cells—BAEC, Normal Skin Fibroblasts—NSF, HepG2 and HumanUmbilical Endothelial Cells—HUVEC-304 (ATCC, USA) were grown in 1.0 gr/lDMEM (Biological industries, Belt-Haemek, Israel), supplemented with 5%FCS, 50 U/ml penicillin, 50 μg/ml streptomycine and 2 mM glutamine. TheBAEC cells were supplemented with complete fibroblast growth factor(Sigma, St. Louis, Mo.). RINr1046-38 (RIN-38) were grown in 199 Earle'ssalts (5.5 mM glucose) medium supplemented with 5% FCS (BiologicalIndustries, Beit-Haemek, Israel), 50U penicillin/ml, 50 μgstreptomycine/ml and 2 mM glutamine.

“HepG2” as used herein refers to ATCC-HB-8065.

“HeLa” as used herein refers to ATCC-CCL-2

“Human Bronchial Epithelial cells” and “B2B” as used herein refers toATCC-CRL-9609.

“HUVEC” and “Human Umbilical Vein Endothelial Cells” as used hereinrefers to ATCC-CRL-1730.

“CHO” and “Chinese Hamster Ovary” as used herein refers to ATCC-61.

Hypoxia Induction

Twenty six hours post transfection or transduction cells were incubatedin an isolated chamber which was washed for 30 minutes by a gas flowcontaining 0.5% O₂, 5% CO₂, balance by N₂. The isolated chamber wasplaced in humidified 5% CO₂, 37° C. incubator.

Luciferase Activity in Cells and Tissues

To assay the PPE-1 promoter activity quantitatively in-vitro andin-vivo, a Luciferase gene expression system kit was employed (PromegaCorp., Madison, Wis.). Forty eight hours post transfection ortransduction the cells were washed and 200 μl lysis buffer was added for15 minutes. Cells lysates were collected and centrifuged for 15 minutes(14,000 rpm) at 4° C. Subsequently, 10 μl of the supernatant was addedto 50 μl Luciferase assay buffer. The activity was measured inLuminometer over a 20 second period.

To assay Luciferase activity in solid tissue a 20 mg sample was excisedand homogenized in 1 ml of the homogenization solution and centrifugedfor 15 minutes (14,000 rpm) at 4° C., and 10 ml of the supernatant wereassayed for Luciferase activity, as described above. Results wereexpressed as Luciferase light units per 1 μg protein. Protein wasmeasured using the Bradford assay with bovine serum albumin (BSA) as astandard.

GFP Activity In-Vitro and In-Vivo

To test GFP expression in-vitro, cells were washed twice with PBS andwere fixed for 30 minutes with freshly made 4% paraformaldehyde in PBS.Following fixation, examination by fluorescent microscopy was conducted.

In order to test the cellular distribution of the delivered genein-vivo, tissues were fixed in freshly made 4% paraformaldehyde in 0.1 Mphosphate buffer for 6 hours at 4° C., soaked overnight in 30% sucroseat 4° C. and frozen in OCT compound (Sakura, USA). The tissue blockswere sliced by a cryostat at 10 μm thickness and observed directly underfluorescence microscopy (FITC filter).

Proliferating and Quiescent Cells

In order to compare the PPE-1 promoter activity in proliferating andquiescent BAEC, the cells were divided into two groups: 1. proliferatingcells—growing and infecting in 10% FCS media. 2. quiescent cells—growingand infected in serum free media started in 72 hours prior to thetransduction.

All cells were grown in humidified incubator, 5% CO₂, 37° C.

Preparation of Recombinant Replication Deficient Adenoviruses

Several recombinant replication deficient adenoviruses (type 5) wereconstructed. An expression cassette including the murinepreproendothelin-1 (PPE-1) promoter (SEQ ID NO:1) located upstream tothe Luciferase gene (originated from pGL2-basic GenBank Accession numberX65323) and the SV40 polyA site (originated from pGL2-basic GenBankAccession number X65323) was ligated into the BamHI restriction site ofpPAC.p1pA (promoter-less construct). The GFP gene (originated frompEGFP, GenBank accession number AAB02572) was ligated to the PPE-1promoter at the Nod restriction site. The replication deficientrecombinant adenoviruses termed Ad5PPE-1Luc or Ad5PPE-1GFP were preparedby co-transfection of pPACPPE-1Luc or Ad5PPE-1GFP with adenovirusplasmid pJM17 as described by Becker, T. C. et al. (Methods Cell biol.43, Roth M. (ed). New York. Academic Press, 1994, pp. 161-189) followedby harvest of recombinant virions.

Viruses were prepared for large-scale production. The viral stocks werestored at 4° C. at concentration of 10⁹-10¹² plaque-forming units/ml(pfu/ml). The viruses Ad5CMV-Luc and Ad5CMV-GFP (Quantumbiotechnologies, Carlsbad, Canada) containing the cytomegalovirus (CMV)immediate early promoter (GenBank Accession number U47119) were preparedfor large scale preparation as described for the PPE-1 viral vectors andwere used as a non-tissue specific control.

Modifications of the PPE Promoter

The modified murine PPE-1 promoter was developed by inserting threecopies of the positive transcription element discovered by Bu et al (J.Biol Chem. (1997) 272(19): 32613-32622) into the NheI restriction enzymesite located downstream (−286 bp) to the 43 base pairs endogenouspositive element (−364 to −320 bp).

The enhancer fragment termed herein “3×” is a triplicate copy of anendogenous sequence element (nucleotide coordinates 407-452 of SEQ IDNO:1) present in the murine PPE-1 promoter. It has been previously shownthat induction of PPE-1 promoter activity in vascular endothelial cellsdepends on the presence of this element Bu et al J. Biol Chem. (1997)272(19): 32613-32622). The 3× fragment was synthesized by using twocomplementary single stranded DNA strands 96 base pares in length(BioTechnology industries; Nes Tziona, Israel), (SEQ ID NO: 2 and 3).The two single stranded DNA fragment were annealed and filled usingKlenow fragment (NEB); the resulting double stranded DNA was 145 basepairs long and included Nhe-1 restriction sites (SEQ ID NO: 4).

The 3× fragment was ligated into the murine PPE-1 promoter down streamof endogenous Nhe-1 site using T4 Ligase. The resulting construct waspropagated in DH5 alpha compatent cells and a large-scale plasmidpreparation was produced using the maxi-prep Qiagene kit.

Additional Plasmids

Wild Type PPE-I Promoter

The PPE-1-Luciferase cassette (5249 bp) containing 1.4 kb of the murinepreproendothelin-1 (PPE-1) promoter, the Luciferase gene with an SV40polyA signal (GenBank Accession number X 65323) site and the firstintron of the murine ET-1 gene is originated from the pEL8 plasmid (8848bp) used by Harats et al (J. Clin. Inv. (1995) 95: 1335-1344). ThePPE-1-Luciferase cassette was extracted from the pEL8 plasmid by usingthe BamHI restriction enzyme, following by extraction of the DNAfragment from a 1% agarose gel using an extraction kit (Qiagen, Hilden,Germany).

The Promoter-Less pPAC.p1pA Plasmid

The promoter-less pPAC.p1pA plasmid (7594 bp) containing sequences ofthe adenovirus type 5 was originated from the pPACCMV.pLpA (8800 bp).The CMV promoter, the multiple cloning site and the SV40 polyadenylationsite (1206 bp) were eliminated by NotI restriction enzyme, Thefragmented DNA was extracted from 1% agarose gel. The linear plasmid(7594 bp) was filled-in by Klenow fragment and BamHI linker was ligatedby rapid DNA ligation kit to both cohesive ends. The linear plasmid wasre-ligated by T4 DNA ligase and transformed into DH5α competent cells,in order to amplify the pPAC.p1pA with the BamH1 restriction sites. Theplasmid was prepared for large-scale preparation and purified by maxiprep DNA purification kit.

pPACPPE-1Luciferase Plasmid

The pPACPPE-1Luciferase plasmid was constructed by inserting thePPE-1-Luciferase cassette into the BamHI restriction site of thepPAC.p1pA plasmid, by using T4 DNA ligase. The plasmid was subsequentlyused to transform DH5α competent cells. The plasmid (12843 bp) wasprepared for large-scale preparation and purified by maxi prep DNApurification kit.

pPACPPE-1GFP Plasmid

The pPACPPE-1GFP plasmid was constructed by sub-cloning the GFP gene(originated from pEGFP, GenBank accession number AAB02572) downstream tothe PPE-1 promoter into the NotI restriction site, by T4 DNA ligase.

The plasmid was subsequently used to transform DH5α competent cells. Theplasmid (11,801 bp) was prepared for large-scale preparation andpurified by maxi prep DNA purification kit.

pACPPE-13× Luciferase and pACPPE-13×GFP Plasmids

The pPACPPE-1-3× Luciferase and pPACPPE-1-3×GFP were constructed byinserting the PPE-1-3×Luc or PPE-1-3×GFP cassette digested by BamHIrestriction to enzyme from pEL8-3× (FIG. 26B) containing Luc or GFP intothe BamHI restriction site of the pPAC.p1pA plasmid. pEL8-3× containsthe modified murine PPE-1 promoter (1.55 kb) (red)—located between BamHIand NotI that contains the triplicate endothelial specific enhancer 3×(as set forth in SEQ ID NO.: 7) located between two NheI site. Thepromoter, the Luciferase or GFP gene, the SV40 poly A sites and thefirst intron of the endothelin-1 gene, all termed the PPE-1 modifiedpromoter cassette was digested and extracted by BamHI restriction enzymeas described in materials and methods. The plasmids (12843 bp) wereprepared for large-scale preparation and purified by maxi prep DNApurification kit.

In-Vitro Experiment, DNA Transduction

Cells were plated in 24 or 96 well dishes 24 hours prior totransduction. Subconfluent cells were counted in a sample well.Thereafter, growth media was aspirated from each well, and the indicatedviral vectors, at the indicated multiplicity of infection (MOI), werediluted in infection media (DMEM or RPMI 1640, 2% FBS) and added to themonolayers. Cells were incubated for 4 h at room temperature.Subsequently, complete medium was added, and the cells were incubated at37° C., 5% CO₂ for 72 h.

Animals

All animal procedures were approved by the “Animal Care and UseCommittee” of Sheba Medical Center, Tel-Hashomer.

Different mouse strains were used:

(i) Male, 3 months old, wild type C57BL/6 mice (Harlan farms, Jerusalem,Israel).

(ii) Male 3 month old BALB/C mice (Harlan farms, Jerusalem, Israel).

(iii) Male and female 6 month old ApoE gene deficient mice hybrids ofC57BL/6×SJ129 mice (Plump A S. et al. Cell (1991) 71:343-353).

(iv) Male and female 3 month old over-expressing the Luciferase geneunder the control of murine PPE-1 promoter (5.9 Kb), generated by Haratset al. (J. Clin. Inv. (1995) 95: 1335-1344).

All mice were grown in the Lipids and Atherosclerosis ResearchInstitute.

Tissue Gene Expression in Normal Mice

To assay the efficiency and tissue specificity, 10¹⁰ pfu/ml ofAd5PPE1Luc or Ad5CMVLuc (as non-tissue-specific control), were suspendedin 100 μl of physiological saline and injected into the tail vein ofmice as described hereinabove. Luciferase activity was assayed 1, 5, 14,30 and 90 days post-injection. To localize cellular distribution of theexpressed reporter genes, Ad5PPE-1 GFP or Ad5CMVGFP (10¹⁰ pfu/ml in 100μl physiological saline) were injected into the tail vein of normal 3month old, male C57BL/6 mice. GFP expression was detected five dayspost-injection. All mice appeared healthy and no toxicity orinflammation was noted in the liver or other tissue.

GFP Activity in Tissues

To test the cellular distribution of the delivered gene in-vivo, tissuesamples from injected mice were fixed in freshly made 4%paraformaldehyde in 0.1 M phosphate buffer for 6 hours at 4° C., soakedovernight in 30% sucrose at 4° C. and frozen in OCT compound (Sakura,Calif., USA). The tissue blocks were sliced at 10 μm thickness andobserved directly under fluorescence microscopy (FITC filter).

Tumor Implantation:

Lewis Lung Carcinoma cells (LLC) were harvested with trypsin/EDTA,washed 3 times with PBS and counted with 0.1% trypan blue (Biologicalindustries, Beit-Haemek, Israel) to assess their viability. In order totest the level of activity of the PPE-1 promoter activity in tumorangiogenesis in mice, two different tumor models were used.

In the primary tumor model, the cells (1×10⁶ cells/ml in 100 μlphysiological saline) were subcutaneously injected to the mice backs(n=17). Twenty-one days post injection Ad5PPE-1, Ad5PPE-1GFP, Ad5CMV, orAd5CMVGFP (10¹⁰ pfu/ml) were injected into the tumor tissue (IT) orintravenously and their activity was detected as described above.

In the metastatic tumor model, the cells (5×10⁵ cells/ml in 50 μlphysiological saline) were injected to the mice foot-pad (n=12). Whenthe tumor tissue reached a size of 0.7 mm in diameter, the foot pad(with the primary tumor) was resected under anaesthetic and sterileconditions. Fourteen days post surgery the viruses (Ad5PPE-1,Ad5PPE-1GFP, Ad5CMVLuc or Ad5CMVGFP) were injected to the mouse tailvein.

In both tumor experimental models mice were sacrificed 5 days post viralinjection, their tissues were excised and tested for Luciferase or GFPactivities.

Wound Healing Model

Male 3 month old C57BL/6 mice were anaesthetized by subcutaneousinjection of sodium pentobarbital (6 mg/kg). Their backs were shaved and5 cm of straight incisions was made. The incisions were immediatelysutured by 4/0 sterile silk thread. The angiogenic process in thehealing wound was examined every two days by H&E and anti von-Willebrandantibody immunohistochemistry staining.

Ten days post incisions 10¹⁰ pfu/ml of Ad5PPE-1Luc or Ad5CMVLuc weresystemically injected to the tail vein. Five days post injections themice were sacrificed and Luciferase activity was assayed as describedabove in the skin of the incision site and in the normal contra lateralsite as a control.

Histological Examination

In order to evaluate the extent of angiogenesis in tumor andmetastasized tissue, the tissues were sliced into 5 μm sections andstained with Haematoxylin and Eosin (H&E). Anti CD31 (rat anti mouseCD31 monoclonal Ab. Phaminogen, N.J., USA) antibodies were used foranalyses of neo-vascularization in the tumor models.

Plasmids and Adenoviral Vectors for VEGF and PDGF-B TransgenicExpression

Recombinant replication-deficient adenoviruses serotype 5 wereconstructed as described in Varda-Bloom, N. et al. [Tissue-specific genetherapy directed to tumor angiogenesis. (2001) Gene Ther 8, 819-27].Briefly, pACCMV.pLpA plasmid was modified to include either the cDNA formurine VEGF₁₆₅ (GenBank Accession number M95200) or rat PDGF-B (GenBankAccession number AF162784), under the regulation of the cytomegalovirus(CMV) immediate early promoter. The pACPPE-1-3× plasmids, in which theCMV promoter was replaced by the modified murine preproendothelin-1(PPE-1-3×) promoter, were constructed with the same cDNA sequences. Eachof the plasmids was co-transfected with pJM17 plasmid into HEK293 cells,to generate the various recombinant adenoviruses. The viruses werepropagated in HEK293 cells and reduced to a concentration of 10¹⁰PFUs/ml. Control vectors were generated similarly.

Mouse Model of Hind Limb Ischemia and Gene Therapy

Male and female C57B16 mice (Harlan Laboratories Ltd., Israel), at least12 weeks of age, were maintained in accordance with guidelines of theAnimal Care and Use Committee of Sheba Medical Center. Hind limbischemia was induced based on previously described protocol [Couffinhal,T. et al. Mouse model of angiogenesis. Am J Pathol 152, 1667-79.(1998)]. In brief, animals were anesthetized with pentobarbital sodium(40 mg/kg, IP). Following shaving of the limb for the right femoralartery was ligated, proximal to the bifurcation of the saphenous andpopliteal arteries. Five days following ligation, 10⁹ PFUs of thevarious adenoviral vectors were I.V. administrated.

Ultrasonic Imaging

Ultrasonic imaging was performed at 7 days intervals following ligationusing Synergy ultrasound system (General Electric, USA) at 7.5 MHz inangiographic mode. Animals were awake and restrained while imaging.Animals were accommodated under conventional conditions for up to 90days.

Immunohistochemistry

Skeletal muscles from both hind limbs and liver tissue of sacrificedischemic mice were frozen in OCT compound and cryo-sectioned.Endothelial cells were immunostained using rat monoclonal anti-CD31antibodies (PharMingen, San Diego, Calif.). Smooth muscle cells wereimmunostained using mouse polyclonal anti-α-SMactin antibodies (SIGMA,St. Louis, Mo.). Background was stained with hematoxylin.

In-Situ Hybridization

5 μm skeletal muscle sections were prepared from both hind limbs ofischemic animals. In-situ hybridization with either sense or antisenseDIG-labeled probes to VEGF₁₆₅ or PDGF-B was performed, and digoxigenin(DIG) was detected by anti-DIG-AP conjugate (Roche MolecularBiochemicals, Mannheim, Germany). Background was stained with methylgreen.

Image Processing

Ultrasonic images were processed using the Image-Pro Plus software tools(Media Cybernetics, Silver Spring, Md.). Number of colored pixelsindicating the most intensive perfusion was calculated for each image.

Statistical Analysis

Analysis between groups for statistically significant differences wasperformed with the use of t-test ANOVA, or the Mann-Whitney Rank test.Data are shown as mean±SE.

Experimental Results Example 1 In-Vitro Assay for Pro-Apoptotic GeneActivity in Endothelial Cells (BAEC) and 293 Cells

In cancer treatment, anti-angiogenic therapy targets the evolvingvasculature which nourishes the growing tumor [Folkman J. N Engl J Med(1995) 333(26):1757-63]. As the research of apoptosis, or programmedcell death, has progressed, numerous genes that encode selective andefficient cell death regulators have been identified [Strasser et al.Annu Rev Biochem (2000) 69:217-45].

The present study screened several pro-apoptotic genes in order toidentify an agent most suitable for anti-angiogenic therapy. Severalpro-apoptotic genes including MORT1 (FADD—Fas associated death domainprotein, GenBank Accession number NM_(—)003824), RIP(receptor-interacting-protein, GenBank Accession number U25995), CASH(c-FLIP, GenBank Accession number AF010127), MACH (caspase 8 GenBankAccession number X98172), CPP32 (caspase 3, GenBank Accession numberU13737), caspase 9 (U60521) and Fas-chimera (Fas-c), a previouslydescribed fusion of two “death receptors”, constructed from theextracellular region of TNFR1 and the trans-membrane and intracellularregions of Fas [Boldin M P et al. J Biol Chem (1995) 270(14):7795-8, seeFIG. 1 a) were PCR amplified and cloned into the pcDNA3 (Invitrogen,Inc.) mammalian expression vector using well known prior art cloningtechniques.

These pro-apoptotic gene constructs were co-expressed along with pGFP inBAEC (Bovine Aortic Endothelial Cells) and 293 cells, which were used asnon-endothelial control cells. 24 hours post transfection, cells wereanalyzed using fluorescent microscopy. Apoptotic cells were identifiedbased on typical morphology, (i.e., small and round shape) usingfluorescence microscopy (FIGS. 2 a-b). Further assessment of theapoptotic phenotype was effected using electron microscopy (FIGS. 3a-f). Quantification of the apoptotic effect showed that MORT1, TNFR1and Fas-chimera induced the highest apoptotic activity in BAEC and 293cells (FIG. 4 a-b). Caspase 3 and 9 were less potent in this respect,probably because they were in an inactive zymogen form. Based on theseresults, the Fas-chimera (Fas-c) gene was selected for the generation ofan adenoviral-vector to be used in anti-angiogenic therapy.

Example 2 Production of Recombinant Adenoviruses Encoding Fas-ChimeraUnder the Control of the Modified PPE-1 Promoter (PPE-1(3×))

A cDNA encoding a full length Fas-chimera was subcloned into the plasmidpPACPPE1-3× containing the modified pre-proendothelin1 promoter (seeFIG. 1 b). Recombinant adenoviruses were produced by co-transfection ofthis plasmid with pJM17 plasmid into human embryonic kidney 293 cells.Successful viral cloning was verified via PCR amplification (FIG. 5 a).

In order to determine the expression of Fas-c in the target cells,endothelial BAEC cells were transduced with the indicated titer ofAd-PPE-1(3×)-Fas-c. 72 h post transduction cells were lysed and cellularproteins resolved using a non-reducing SDS-PAGE gel. Western blotanalysis was performed using anti-TNFR1 antibody (Sc-7895, Santa-CruzBiotech). As demonstrated in FIG. 5 b, a prominent band migrating at 45kD was clearly evident and its expression was dose-dependent, suggestingcorrect folding and expression of the chimeric protein. In contrast, nocorresponding bands were evident in non-transduced endothelial cells orin cells transduced with control empty viral vector. Thus, these resultsconfirmed that the adenoviral-mediated gene transfer of Fas-c results intransgene expression in the target cells.

Example 3 Ad-PPE-1(3×)-Fas-c Expression Induces Apoptosis in EndothelialCells

The ability of Ad-PPE-1(3×)-Fas chimera to induce apoptosis ofendothelial cells was determined. As shown in FIGS. 6 a-b,pre-proendothelin directed, adenovirus-mediated transduction ofendothelial cells resulted in an evident and massive cell death; HUVECand BAEC infected with Ad-PPE-1(3×)-Fas-c (10³ MOI) had morphologicalfeatures of adherent cells undergoing apoptosis including membraneblebbing, rounding and shrinking and detachment from the culture dish.In contrast, cells infected with control viruses at the same MOI,maintained normal appearance and growth rate. Cells transduced with 100MOI presented only a minimal degree of cell death (data not shown).

Further assessment of the cytotoxic properties of Ad-PPE-1(3×)-Fas-c waseffected by expressing this virus in cells expressing the reporter geneGFP under the control of the PPE-1 promoter. As is evident from FIGS. 6c-d, most of the transduced cells acquired a typical apoptoticappearance 72 hours following transduction, whereas cells co-transducedwith control virus and Ad-PPE-GFP appeared normal.

The cytotoxic effect of Fas-c was quantified using crystal violetstaining. As shown in FIG. 7, infection of BAEC and HUVEC withAd-PPE-Fas-c resulted in mortality rates of 57% and 65%, respectively,while the control virus did not affect cell viability.

The endothelial cell specificity of the pro-apoptotic vectorAd-PPE-Fas-c was demonstrated by infecting NSF (normal skin fibroblasts)with this vector. These cells, which express low levels of PPE-1[Varda-Bloom, N. et al. Gene Ther 8, 819-27, (2001)] were not affectedby infection with Ad-PPE-Fas-c. In contrast, the recombinant vectorAd-CMV-Fas-c induced apoptotic in these cells.

Example 4 Co-Administration of Ad-PPE-1(3×)-Fas-c Receptor and TNFαLigand Augments the Pro-Apoptotic Effect in a Selective Manner

The ability of TNFα to augment the apoptotic effect in Fas-c expressingcells was investigated. Human TNFα was added to an endothelial cellculture 48 h-post virus infection with Ad-PPE-Fas-c (M01 of 100). Cellviability was assayed 24 h later. As shown in FIG. 8, TNFα (10 ng/ml)induced a 73% decrease in viability of Ad-PPE-1(3×)-Fas-c infectedcells, whereas no significant mortality was effected by TNFα alone or incells infected with control virus (Ad-Luc).

To substantiate the effect of TNFα, cell specificity was addressed. NSF(normal skin fibroblasts), DA3 (mouse mammary adenocarcinoma), D122(Lewis lung carcinoma) and B16 melanoma cells were infected withAd-PPE-Fas-c or a control virus. 48 hours later, culture wassupplemented with TNFα and cell morphology was assessed followingstaining with crystal violet. As shown in FIGS. 9 a-e, non-endothelialcells infected with Ad-PPE-Fas-c displayed normal appearance and werenot affected by TNF. On the other hand, adenoviral mediated infection ofBAEC with Fas-c resulted in marked decrease in cell viability when TNFwas added. The non-selective apoptotic activity of Fas-c driven by CMVpromoter is demonstrated in FIG. 10 a which illustrates theTNF-dependent apoptotic effect of Ad-CMV-Fas-c on endothelial cells.Viability of BAEC cells infected with the indicated MOI ofAd-CMV-Fas-chimera was determined following incubation with TNF.

Notably, the non-endothelial-specific vector Ad-CMV-Fas-c causedTNFα-dependent apoptosis of both endothelial and non-endothelial cells(FIGS. 10 b-d).

Example 5 Ad-PPE1(3×)-Fas-c Induces In-Vivo Growth Retardation of B16Melanoma in Mice

The B16 melanoma mouse model was used in order to test the anti-tumoraleffect of Fas-c expressed from the PPE1-3× promoter. B16 melanoma cells(8×10⁵) were injected subcutaneously to the flank region of 40 C57bl/6mice. When the tumor was palpable (^(˜)5×5 mm), the mice were randomizedinto 4 groups as follows: (i) control—saline injection; (ii) controlvirus (Adeno virus containing luciferase controlled by PPE promoter);(iii) Ad-PPE1-3×-Fas-c-virus containing the Fas-TNF receptor chimericgene controlled by the preproendothelin (PPE) promoter; and (iv)Ad-CMV-Fas-c-virus containing the Fas-TNF receptor chimeric genecontrolled by the non-endothelial specific, CMV promoter.

Tumor size (length and width) was measured using a hand caliper. Asshown in FIG. 11 a, tumor size was lower for mice treated withAd-PPE1-3×-Fas-c or Ad-CMV-Fas-c as compared to control mice. Tumorweights at the end of the treatment period was also lower in theAd-PPE1-3×-Fas-c treated mice (FIG. 11 b). Mice injected withAd-PPE1-3×-Fas-c showed marked necrosis of their tumor (FIG. 11 c).

Inhibition of Metastatic Disease: Lewis Lung Carcinoma Model:

Specificity of expression and efficacy of inhibition of tumor growthwith PPE-1(3×)-Fas-c chimera was further tested in the metastatic LewisLung Carcinoma model. Lung LLC metastases were induced in male C57BL/6Jas described in detail hereinbelow, and mice were injected with theviral vectors AdPPe-1(3×) LUC, AdPPE-1(3×)-Fas-c, and AdCMV-Fas-c twice,at 9 day intervals (Greenberger et al, J Clin Invest 2004;113:1017-1024).

Organs were harvested from the mice 6 days after viral administration,and assayed for Fas-c expression by PCR. Transcriptional control ofFas-c by PPE-1(3×) promoter led to expression restricted to the tumorbearing lung (results not shown), in stark contrast to the broaddistribution of Fas-c expression in the CMV-Fas-c-treated mice (data notshown, see Greenberger et al, J Clin Invest 2004; 113:1017-1024).

Further, gross pathological inspection of lungs from the treated andcontrol groups revealed that AdPPE-1(3×)-Fas-c administration to themetastases-bearing mice inhibited tumor growth and reduced the size ofgrowing tumors on the lung surface, while the control animals' lungswere almost completely replaced by tumoral tissue (data not shown, seeGreenberger et al, J Clin Invest 2004; 113:1017-1024).

Yet further, histopathology and TUNEL and endothelial-specific CD31staining of lung sections from treated and control mice revealed thatAdPPE-1(3×)-Fas-c administration to the metastases-bearing mice causedmassive apoptosis and necrosis in the tumor tissue, associated withextensive damage to the tumor vascular endothelium. In contrast, theblood vessels of the control treated mice were unaffected (data notshown, see Greenberger et al, J Clin Invest 2004; 113:1017-1024).

Example 6 Analysis of 3×-PPE-1 Plasmid Activity In-Vitro

In order to analyze the activity of the PPE-1-3×, a comparison ofreporter gene expression in the PPE-1-3× promoter plasmid and theunmodified PPE-1 promoter plasmid was undertaken. Reporter gene plasmidscontaining either the PPE-1-3× fragment or the unmodified PPE-1 fragmentand the reporter gene Luciferase were transfected into endothelial andnon-endothelial cell lines as well as to a bronchial epithelium cellline (B2B) which express the PPE-1 promoter (see materials and methodsabove). The B2B cell line was chosen to provide an indication of the 3×element's capacity to reduce expression in non-endothelial cell linesrelative to the PPE-1 promoter. Transfection was accomplished usinglipofectamine (Promega Corp., Madison, Wis.). A β-gal-neo plasmid wasemployed as an indicator of the transfection efficiency in each caseaccording to accepted molecular biology practice.

Forty-eight hours post transfection, the cells were harvested usinglysis buffer (Promega Corp., Madison, Wis.) and Luciferase activity wasanalyzed by a luminometer (TD-20e—Turner Designs, Sunnyvale, Calif.). Inparallel, μgal activity was analyzed in order to standardize fordifferent transformation efficiencies. The results are summarized inFIG. 12 and Table 2. Luciferase activity under the control of PPE-3× is15-20 times higher than Luciferase activity under the control of theunmodified PPE-1. In non-endothelial cell lines minimal expression wasdetected using both the PPE-1 and PPE-1-3×. This demonstrates thatPPE-3× is a promising candidate for delivery of a gene specifically intoendothelial cells in-vivo.

TABLE 2 Luciferase activity in cells transfected with PPE-1 and PPE-1-3XLuciferase constructs Luciferase activity in: endothelial cell lines nonendothelial Plasmid HUVAC BAEC cell lines RIN PPE-1 135.12  1121.3 0.73PPE-1-3X 768 18331.7 0.32

Example 7 Activity and Specificity of Ad5PPE-1/Luciferase In-Vitro

The PPE-1/Luciferase, PPE-1-3×/Luciferase, PPE-1/GFP and PPE-1-3×/GFPwere also ligated into the Ad5 plasmid to produce Ad5PPE-1/Luc andAd5PPE-1-3×/luc, Ad5PPE-1/GFP and Ad5PPE-1-3×/GFP (Varda-Bloom et al.,(2001) Gene therapy 8:819-827). These constructs were assayed separatelyas detailed hereinbelow.

In order to test the activity of the Ad5PPE-1/luc, transfections of B2B(Human bronchial epithelial), BAEC (Bovine Aortic Endothelial Cells) andHUVEC (Human Umbilical Vein Endothelial Cells) were undertaken. Thesethree cell lines express the endothelin gene and were chosen to indicatelevels of expression of the tested construct in an endothelial cell. TheRIN (Rat Insulinoma) cell line, which does not express endothelin, wasemployed as a negative control and transfected with the same construct.Ad5CMVLuc (Luciferase under the control of CMV promoter) was used asnon-endothelial-specific control in all cell lines.

FIG. 13 clearly illustrates that higher Luciferase expression wasachieved in endothelial BAEC and HUVEC cell lines with the PPE-1promoter than with the CMV promoter. In the MN cells, which are not ofendothelial origin, the CMV promoter produced more Luciferase activitythan the PPE-1 promoter. These results demonstrate the endothelialspecificity of the un-modified PPE-1 promoter.

Example 8 Activity and Specificity of Ad5PPE-3×Luc and Ad5PPE-3×GFP

The Ad5PPE-3×/Luciferase and Ad5PPE-3×/GFP constructs were used totransfect the cell lines described hereinabove in Example 7 in order toascertain the impact of the 3× element on specificity and expressionlevels. As in example 7, Ad5CMVLuc was used as anon-endothelial-specific control. Higher Luciferase expression in BAECand HUVEC cell lines was detected under the control of the PPE-3×promoter as compared to the CMV promoter.

FIG. 14A is a photomicrograph illustrating GFP expression under thecontrol of Ad5PPE-1-3× in the BAEC cell line. FIG. 14B is aphotomicrograph illustrating GFP expression of Ad5CMV in the BAEC line.As is clearly shown by these Figures, the PPE-1-3× promoter is moreactive in endothelial cells. These results clearly indicate that the 3×element does not detract from the endothelial specificity of the PPE-1promoter. Relative activities of the PPE-1 and PPE-1-3× promoters incell culture are presented in Example 11 hereinbelow.

Example 9 In-Vitro Assay of Pro-Apoptotic Activity of the p55 Gene

Following sub cloning of P55 (TNFR1, GenBank accession number M75866)into PACPPE3× (containing the PPE-1-3× promoter), and into PACCMV,co-transfection of these plasmids and GFP (pEGFP-C1 vector; CLONTECH,Palo Alto, Calif.). was performed as described hereinabove. Briefly, thegene was subcloned downstream to the PPE-1 promoter (instead of theluciferase gene) into the NotI restriction site, by T4 DNA ligase,following by transforming it into DH5α competent cells. Twenty fourhours post-transfection, small and rounded apoptotic cells were visuallydiscernible from normal cells. Electron microscopy of cells transfectedwith the pro-apoptotic plasmids showed typical appearance of apoptosis,confirming the visual evaluation.

Under the control of the PPE-1-3× promoter, apoptosis was induced by p55only in endothelial cells (FIG. 15), whereas the CMV promoter did notshow any cell specific activity. Luciferase under the control ofPPE-1-3× did not induce apoptosis in any tested cell lines. Theseresults indicate that by employing the PPE-1-3× promoter, it is feasibleto induce apoptosis specifically in endothelial cells.

Example 10 Hypoxia Responsive Element (HRE) can Enhance Target GeneExpression in Hypoxic Sensitive Endothelial Cells

Hypoxia is an important regulator of blood vessels' tone and structure.It has also been shown to be a potent stimulus of angiogenesis (in bothischemic heart diseases and cancer (Semenza, G. L. et al. (2000) Adv ExpMed Biol.; 475:123-30; Williams, K. J. (2001) Breast Cancer Res. 2001:3; 328-31 and Shimo, T. (2001) Cancer Lett. 174; 57-64). Further,hypoxia has been reported to regulate the expression of many genesincluding erythropoietin, VEGF, glycolytic enzymes and ET-1. These genesare controlled by a common oxygen-sensing pathway, an inducibletranscription complex termed hypoxia inducible factor-1 (HIF-1). TheHIF-1 complex mediates transcriptional responses to hypoxia by bindingthe cis acting hypoxia responsive element (HRE) of target genes. The HREis a conserved sequence located in the promoters of few genes thatrespond to hypoxia including: VEGF, Nitric Oxide Syntase-2,erythropoietin and others including endothelin-1, ET-1. The ET-1promoter contains an inverted hypoxia response element at position −118bp upstream of the transcription start site, the element contain 7 basepairs and is located between the GATA-2 and AP1 sites 5′ GCACGTT 3′—50base-pairs. (SEQ ID NO: 5.)

The preproendothelin-1 (PPE-1) promoter contains an hypoxia responsiveelement (HRE) that has the potential to increase its expression in thehypoxic microenvironment of tumor or ischemic tissues, thus making it“tumoral tissue specific” and/or “ischemic tissue specific”. In orderevaluate the actual function of this HRE, assays of the PPE-1 promoterand PPE-1-3× promoter in conjunction with a Luciferase or GFP reportergene and delivered by an adenoviral vector were undertaken.

Luciferase activity under the control of the PPE-1 promoter or thePPE-1-3× promoter was compared in BAEC cells under normoxic and hypoxicconditions (0.5% O₂ for 16 h). The Luciferase activity under the controlof PPE-1 promoter was 5 times higher when exposed to hypoxia (FIGS. 16and 17). Further, the Luciferase activity under the control of PPE-1-3×promoter was 2.5 times higher under hypoxic conditions. In summary,introduction of the 3× element into the PPE 1 promoter is till capableof increasing expression levels of a downstream gene in response tohypoxia, even though the normoxic levels of expression with the PPE-1-3×gene are higher than those observed with the unmodified PPE-1 promoter.

Example 11 Further Evaluation of PPE-1-3× and PPE-1 Promoter Activity inEndothelial Cell Lines

FIG. 18 summarizes the results from B2B, HUVEC and BAEC transfectionexperiments using pPPE-1/Luciferase and pPPE-1-3×/Luciferase. HigherLuciferase expression (30, 8.5 and 1.5 times more) was observed underthe control of the PPE-1-3× promoter than under the PPE-1 promoter inB2B, HUVEC and BAEC, respectively. These results confirm those presentedhereinabove and serve to establish that PPE-1-3× is well suited todirecting high level expression specifically to endothelial cells. Inthe context of future in-vivo delivery, the higher levels of expressionachieved with the PPE-1-3× construct translate into administration ofsmaller amounts of DNA. This, in turn, will serve to increasespecificity even further.

Example 12 Efficiency, Specificity and Stability of Ad5PPE-1Luc In-Vivo

In order to confirm that the endothelial specificity of expressionobserved in examples 7 through 10 was not an artifact of cell culture,the Ad5PPE-1/Luciferase construct was injected into C57BL/6 mice asdescribed hereinabove in “Tissue gene expression in normal mice”. As inthe in-vitro studies, Ad5CMV/Luciferase was employed as a negativecontrol.

Following injection of adenoviral vectors, the specific activity andstability of Luciferase in vascularized and non-vascularized tissues wasassayed. Results are summarized in FIG. 19 (Luciferase expressionrelative to expression in liver) and Table 3 (Luciferase expression as apercentage of total expression in the body). As expected, inAd5CMV/Luciferase treated mice most of the Luciferase activity (>80% ofthe total body expression) was found in the liver. Luciferase activitycontrolled by the PPE-1 promoter was lower in the liver (37-54% of thetotal body expression). The PPE-1 derived expression was much higher inthe aorta (23-33% of the total body expression 5 and 14 days postinjection, respectively), compared to Ad5CMV/Luciferase. treated mice(up to 1.8% of total body expression; Table 2). These results confirmthe endothelial specificity observed in cell culture. It should beremembered that the liver is a highly vascularized organ. Thereforeexamination of cellular expression within organs was undertaken, asdetailed hereinbelow.

TABLE 3 Luciferase expression in organs 5 and 14 days post injection ofPPE-1 and CMV based constructs Day post 5 14 injection Light units/μgprotein Light units/μg protein Organ PPE-1 CMV PPE-1 CMV Aorta 13.0 ±2.9 1.4 ± 0.5 10.6 ± 2.4 1.3 ± 0.3 (32.7%) (0.56%) (12.6%) (1.1%) Heart0.2 ± 0.1 1 ± 0.6 1.5 ± 0.3 1.8 ± 0.6 (0.5%) (0.4%) (1.7%) (1.6%) liver22.7 ± 4.5 219 ± 111.5 34.9 ± 7.8 52.8 ± 10.6 (57%) (88.6%) (41.6%)(46.8%) lung 0.2 ± 0.1 2.3 ± 1.0 3.6 ± 0.8 2.0 ± 0.9 (0.5%) (0.9%)(4.3%) (1.8%) muscle 0.3 ± 0.1 0.8 ± 0.2 1.2 ± 0.3 1.5 ± 0.5 (0.7%)(0.3%) (1.4%) (1.3%) spleen 1.3 ± 0.8 1.6 ± 0.9 2.0 ± 0.4 2.3 ± 0.9(3.2%) (0.6%) (2.4%) (2.0%) pancreas 2 ± 0.6 20.1 ± 6.8 26.4 ± 5.9 45.2± 24.5 (5.0%) (8.1%) (31.5%) (40.1%) kidney 0.1 ± 0 0.9 ± 0.6 0.6 ± 0.10.8 ± 0.3 (0.25%) (0.4%) (0.71%) (0.7%)

FIGS. 41A and 41 B demonstrate the absolute Luciferase activity (lightunits/μg protein) in the aortas (A) and livers (B) of the 110 injectedmice. Luciferase activity was measured 1 (n=13), 5 (n=34), 14 (n=32), 30(n=20) and 90 (n=11) days post injection. The results in the aortarepresent the promoters (PPE-1 or CMV) activity mostly in endothelialcells, while the results in the livers represent their activity mostlyin hepatocytes.

Example 13 Assays of Efficiency, Specificity and Stability of Ad5PPE-1In-Vivo—in BALB/C Mice

The experiments of example 12 were repeated in 12 week old BALB/C mice(n=10 for each group) in order to demonstrate that the observed resultswere not an artifact of a particular strain of animals.

Because Absolute results with the adenoviral vectors were lower inBALB/C mice than in C57BL/6 mice, the Luciferase expression is expressedas percentage of the total Luciferase activity in all tissues.

The highest relative Luciferase expression 5 days post injection wasobserved in the spleens of Ad5PPE-1 (90.9%), and in the livers of Ad5CMV(86.2%) injected mice. A significant increase in the relative Luciferaseactivity in the aortas of Ad5PPE-1 injected mice 14 days post injection(32.9%), compared to its activity five days post injection (1.75%) wasalso observed (FIGS. 42A and 42B; Ad5PPE-1Luc—open bars; Ad5CMVLuc-blackbars).

These results confirm that regardless of mouse strain, the tissuespecificity of the PPE-1 promoter is sufficiently strong to effectivelyeliminate hepatocyte expression, despite preferential uptake of injectedDNA by hepatocytes.

Example 14 Cellular Localization of Gene Delivered by Ad5PPE-1 In-Vivo

In order to ascertain cellular expression sites of the gene expressed byPPE-1 in-vivo, Green Fluorescent Protein (GFP) delivered by theadenoviral vector Ad5PPE-1-GFP was used. Ad5CMVGFP (Quantum, Canada) wasused as non-endothelial-cell-specific negative control. Five dayspost-intravenous injection the mice were sacrificed and their tissueswere analyzed by fluorescent microscopy.

In the mice injected with Ad5CMVGFP vector, most of the expression wasdetected in the hepatocytes, and no expression was detected inendothelial cell in the liver (FIG. 20A). In sharp contrast,Ad5PPE-1-GFP injected mice (FIG. 20B), showed no expression inhepatocytes, but significant expression in endothelial cells in theblood vessels of the liver. Similar results were obtained in othertissues where practically all the PPE-1 derived expression was detectedin the endothelium, while none of the CMV derived expression wasendothelial. These results indicate endothelial specificity is preservedeven within an organ containing endothelial and non-endothelial cells.This finding has important implications for prevention of angiogenesisin growing tumors.

Example 15 Assays of Efficiency and Endothelial Specificity ofAd5PPE-1-3×Luc and Ad5PPE-1-3×GFP In-Vitro

In order to determine the relative efficacy of Ad5PPE-1 and Ad5PPE-1-3×in driving expression of the reporter genes Luciferase and greenfluorescent protein (GFP) in cells, specific activity in endothelialcells was tested in-vitro using cell lines described hereinabove.Ad5CMVLuc and Ad5CMVGFP were employed as non-tissue specific controls.Ad5PPE-1Luc and Ad5PPE-1GFP were employed to ascertain the relativechange in expression level caused by addition of the 3× sequence.

Results, summarized in FIGS. 21 and 22, indicate that Luciferaseactivities under the control of the PPE-1-3× promoter were 5-10 timeshigher in EC lines (Bovine Aortic Endothelial Cells—BAEC) compared toactivity in non-endothelial cells—Rat Insulinoma—RIN, HeLA, HePG2 andnormal skin fibroblasts (NSF) (FIGS. 21 and 22).

FIG. 21 shows Luciferase activity as light units/μg protein in B2B, BAECand RIN cells transduced by Ad5PPE-1Luc, Ad5PPE-1-3×Luc, and Ad5CMVLucHighest Luciferase expression was observed in RIN cells transduced byAd5CMVLuc, however this construct was poorly expressed in BAEC and B2Bcells. The next highest level of Luciferase expression was observed inBAEC cells transduced by Ad5PPE-1-3×Luc. Ad5PPE-1Luc was expressed atlower levels in BAEC cells. In the B2B cell line Ad5PPE-1Luc andAd5PPE-1-3×Luc were expressed at nearly identical levels.

Overall, luciferase activity in the endothelial cell lines under thecontrol of PPE-1-3× promoter was 23 times higher than under the controlof PPE-1 promoter and 23-47 times higher than under the control of theCMV promoter at the same infection conditions (moi=10). This is despitethe fact that Luciferase expression in non-endothelial RIN cells was3000 times higher under the control of the CMV promoter (FIG. 21).

In order to establish that PPE-1 and PPE-1-3× are inactive in othernon-endothelial cell lineages HeLA, HepG2, NSF cell lines weretransduced. BAEC was employed as an endothelial control. FIG. 22 showsLuciferase activity as light units/μg protein in HeLA, HepG2, NSF andBAEC cells transduced by Ad5PPE-1Luc, Ad5PPE-1-3×Luc and Ad5CMVLuc.Transduction with Ad5CMVLuc caused high levels of Luciferase expressionin HeLA, HepG2 and NSF cells. These cell lines failed to expressLuciferase under the control of PPE-1 and expressed Luciferase at lowlevels with the PPE-1-3× promoter. As expected, BAEC cells transducedwith Ad5PPE-1Luc or Ad5PPE-1-3×Luc exhibited high Luciferase expression.

Taken together these results indicate that introduction of the 3×sequence into the PPE-1 promoter caused higher levels of expression inendothelial cell lines while preventing unwanted expression innon-endothelial cells.

Addition of the 3× sequence to the PPE-1 promoter also increased levelsof Green fluorescent protein expression in EC lines (Bovine AorticEndothelial Cells—BAEC) as indicated in FIGS. 23 A-C which depicts GFPexpression in BAEC transduced by moi=1. No expression of GFP wasobserved using a CMV promoter in this experiment.

In FIG. 23, panel A indicates Ad5PPE-1-3×GFP transduced cells, panel Bindicates Ad5PPE-1GFP transduced cells and panel C indicates Ad5CMVGFP.Again, introduction of the 3× sequence into the PPE-1 promotersignificantly increased expression of the reporter gene. This resultindicates that the ability of the 3× sequence to function as anendothelial specific enhancer is not a function of the downstream genebeing transcribed.

Moreover, Ad5PPE-1-3×-GFP and Ad5PPE-1GFP transduction resulted in noGFP expression in non-endothelial cells SMC, HeLa, HePG2 and normal skinfibroblasts (NSF) compared to the high expression under the CMV promoteras summarized in FIGS. 24-27.

FIG. 24 shows GFP expression in SMC transduced by moi=1 of eitherAd5PPE-1-3×GFP (panel A) or Ad5CMVGFP (panel B). While high level GFPexpression resulted from Ad5CMVGFP transduction, no GFP expressionresulted from transduction with Ad5PPE-1-3×GFP transduction.

FIG. 25 shows results of a similar experiment conducted in HeLa cells.As in the previous Figure, panel A indicates cells transduced withAd5PPE-1-3×GFP and panel B indicates cells transduced with Ad5CMVGFP.Again, while high level GFP expression resulted from Ad5CMVGFPtransduction, no GFP expression resulted from transduction withAd5PPE-1-3×GFP transduction.

FIG. 26 shows results of a similar experiment conducted in HepG2 cells.As in the previous Figure, panel A indicates cells transduced withAd5PPE4(3×)GFP and panel B indicates cells transduced with Ad5CMVGFP.Again, while high level GFP expression resulted from Ad5CMVGFPtransduction, no GFP expression resulted from transduction withAd5PPE-1-3×GFP.

FIG. 27 shows results of a similar experiment conducted in NSF cells. Asin the previous figure, panel A indicates cells transduced withAd5PPE-1-3×GFP and panel B indicates cells transduced with Ad5CMVGFP.Again, while high level GFP expression resulted from Ad5CMVGFPtransduction, very low GFP expression resulted from transduction withAd5PPE-1-3×GFP.

These results, taken together, indicate a high level of endothelialspecificity and a high level of endothelial expression is obtained byusing a modified PPE-1 promoter containing the 3× sequence of SEQ IDNO.: 7.

Example 16 Cellular Localization of a Reporter Gene Delivered byAd5PPE-1-3× In-Vivo

In order to determine the cellular localization pattern of a reportergene expressed under the control of the PPE-1-3× promoter in-vivo,Ad5PPE-1-3×GFP and Ad5PPE-1GFP were injected into mice as describedhereinabove. Five days post-intravenous injection, the mice weresacrificed and their tissues were analyzed by a fluorescent microscopy.

Significantly higher GFP activity was observed in the endothelial cellsof the liver, kidney and spleen blood Vessels of Ad5PPE-1-3×GFP injectedmice compared to the Ad5PPE-1GFP injected mice. FIGS. 28 A-B showrepresentative results.

FIG. 28A shows low level GFP expression in endothelial cells lining ablood vessel of a mouse injected with the Ad5PPE-1GFP. FIG. 28B showsthe much higher level of GFP expression resulting from addition of the3× sequence to the construct.

Despite the high expression in the lining of the blood vessels, noexpression was detected in the hepatocytes, glomeruli, epithelial cellsand splenocytes (FIGS. 18 and 19).

FIG. 29 shows representative results from kidney tissue of injectedmice. Ad5CMVGFP injected mice (FIG. 29A), Ad5PPE-1GFP (FIG. 29 b) andAd5PPE-1-3×GFP (FIG. 29C) injected mice all exhibited low GFP activityin kidney cells. In FIG. 29B, slightly higher GFP expression is visiblein the blood vessel wall (indicated by arrow).

FIG. 30 shows representative results from spleen tissue of injectedmice. Ad5CMVGFP injected mice (FIG. 30A), Ad5PPE-1GFP injected mice(FIG. 30B) and Ad5PPE-1-3×GFP injected mice (FIG. 30 C) all exhibitedlow level GFP activity in cells of the spleen. Higher GFP activity isvisible in the blood vessels of Ad5PPE-1-3×GFP injected mice (indicatedby arrow).

These results confirmed that both the PPE-1 and the PPE-1-3× promoterare endothelial cell specific in-vivo. They further suggest thatactivity of both promoters was limited in non-proliferating endothelialtissue (i.e. blood vessels of healthy organs. Therefore, assays in atumor angiogenic model were undertaken.

Example 17 Assays of the Ad5PPE-1 Construct in Tumor NeovascularizationIn-Vivo

In order to ascertain the ability of AD5PPE to specifically directexpression of a reporter gene to angiogenic blood vessels in a tumor,the murine LLC model (described hereinabove in materials and methods)was employed.

In a one experiment, Luciferase expression in tumor neovascularizationwas tested five days post systemic injections of Ad5PPE-1Luc orAd5CMVLuc (10¹⁰ pfu/ml each).

In this experiment, systemic injection of Ad5CMVLuc to both primary andmetastatic tumor models resulted in minimal expression in the primarytumor or in the metastatic lung. This level of expression was similar tothe minimal expression of Luciferase directed by CMV in naive normallungs (FIG. 35; black bars; n=12). In sharp contrast, under the controlof PPE-1 promoter (FIG. 35; open bars; n=9), the highly angiogenic lungmetastases were associated Luciferase activity which was about 200 timeshigher than the Luciferase activity in the poorly-vascularized primarytumor and the naive lungs.

The Luciferase expression in non-metastatic tissues such as the liver,kidney, heart and pancreas was minimal. The expression level in theaorta was about 30% of the levels in the metastatic lungs.

In an additional experiment in the LLC model Ad5PPE-1GFP and Ad5CMVGFPconstructs were employed to localize reporter gene expression in theprimary tumor and metastatic lungs.

Ad5PPE-1GFP injected mice, showed high levels of GFP specific expressionto in the blood vessels of the primary tumor (FIG. 47C), although noexpression was detected in the tumor cells themselves. This observationis consistent with the results of the LLC cell culture model presentedin example 20. In lung metastases, high levels of GFP expression weredetected in both big arteries and small angiogenic vessels of themetastatic foci (FIG. 47A). No expression was detected in the normallung tissue. The endothelial cell localization was demonstrated byco-localization of the GFP expression (FIG. 47A) and the CD31 antibodyimmunostaining (FIG. 47B). In striking contrast, in Ad5CMVGFP injectedmice, no GFP activity was detectable in both the primary tumor and lungmetastasis.

FIG. 47C illustrates GFP expression in blood vessels of a primary tumorfollowing intra tumoral injection of Ad5PPE-1GFP. FIG. 47D is a phasecontrast image of the same filed as panel C illustrating the tumor andits blood vessels.

These results indicate that while PPE-1 does not drive high levelexpression in tumor cells per se, the promoter does drive high levelexpression in vascular endothelia within the tumor, especially inrapidly proliferating angiogenic vessels.

Intra-tumor injection of Ad5CMV into primary subcutaneous tumor modelresulted in high Luciferase expression in the turner tissue andmoderately levels of expression liver (10% of the amount expressed inthe tumor; FIG. 53). No expression was detected in the metastatic lungs.On the other hand, when injected intra-tumoral, Luciferase expressionunder the control PPE-1 promoter resulted in similar Luciferase levelsof expression in the primary tumor and the metastatic lungs and noexpression was detected in the liver.

Example 18 Assays of the Ad5PPE-1 Construct in a Carcinoma Cell CultureSystem

In order to assay the efficiency of Ad5PPE-1 and Ad5CMV to driveLuciferase expression in cancerous cells, the D122-96 Lewis LungCarcinoma cell line was employed.

In-vitro transduction at varying multiplicities of infection (moi) wasperformed. The results indicate that both adenoviral vectors are able totransduce the Luciferase gene to these cells (Table 4). Nevertheless,Luciferase activity directed by the PPE-1 promoter was much lower in theLLC cells than the activity detected in endothelial cells, 50 vs.1000-2500 light units/μg protein, respectively.

TABLE 4 In-vitro transduction of Lewis lung carcinoma cell line(D122-96) with Ad5PPE-1Luc and Ad5CMVLuc. MOI = 1 MOI = 5 MOI = 10AdPPE-1 8.1 ± 0.06 33.95 ± 7.0 50.7 ± 5.0 Ad5CMV 9.3 ± 1.1 47.3 ± 4.088.13 ± 10.1

Example 19 Assay of the Effect of the 3× Sequence in Tumor AngiogenicBlood Vessels In-Vivo

In order to ascertain the effect of the 3× sequence on the PPE-1promoter in angiogenic blood vessels, the Lewis Lung Carcinoma (LLC)metastases model (described hereinabove in material and methods) wasemployed. Five days post IV injection of 10¹⁰ infectious units ofAd5PPE-1GFP, Ad5PPE-1-3×GFP or Ad5CMVGFP, the mice were sacrificed andtheir tissues were analyzed as described in material and methods.

FIGS. 31 A-D summarize the GFP expression in metastatic lungs of controlmice injected with Saline (FIG. 31A), mice injected with Ad5CMVGFP (FIG.31 B), mice injected with Ad5PPE-1GFP (FIG. 31 C) and mice injected withAd5PPE-1-3×GFP (FIG. 31D). Anti-CD31 immunostaining (FIGS. 31C′ to 20D′)confirm the location of the GFP expression in each metastatic tissue.The results show that while no GFP expression was detected incontrol—saline injected mice (FIG. 31A), there was a slight expressionaround the epithelial bronchi of the CMV injected mice, but not in theangiogenic blood vessels of the metastatic lung of these mice (FIG.31B). Low GFP expression was observed in metastatic lungs of Ad5PPE-1GFPinjected mice (FIGS. 31C and 31C′), while high and specific expressionwas observed in the new blood vessels of Ad5PPE-1-3×GFP injected mice(FIGS. 31D and 31D′).

These results explain the apparent disparity between the in-vivo resultsof Example 15 and the in-vitro results of Examples 7, 8 and 11. Both thePPE-1 and the PPE-1-3× promoter are endothelial specific. However, the3× sequence greatly increases the level of expression in rapidlyproliferating endothelial tissue, such as newly forming blood vessels ina growing tumor.

Example 20 Effect of the 3× Element on the PPE-1 Promoter in TumorAngiogenic Blood Vessels

In order to study the effect of the 3× element of the present inventionon efficacy and specific activity of the PPE-1 promoter in tumorangiogenic blood vessels, the LLC metastases model was employed. Fivedays post i.v. injection of 10¹⁰ pfu/ml of Ad5PPE-1Luc, Ad5PPE-1-3×Luc,Ad5CMVLuc, Ad5PPE-1GFP, Ad5PPE-1-3×-GFP or Ad5CMVGFP, the mice weresacrificed and their tissues were analyzed for Luciferase or GFPexpression as described hereinabove.

FIG. 48 is a histogram comparing Luciferase expression in normal lungsversus that in metastatic lungs following systemic injection ofAd5PPE-1-3×luc, Ad5PPE-1Luc or Ad5CMVLuc. Experimental groups wereAd5CMVLuc (n=7; black bars), Ad5PPE-1Luc (n=6; gray bars) andAd5PPE-1-3×Luc (n=13; brown bars). Activity is expressed as lightunits/μg protein.

Luciferase expression under the control of the PPE-1-3× promoter was 35fold greater in the metastatic lungs relative to its activity in normallungs and 3.5 fold higher than expression driven by the PPE-1 promoterwithout the 3× element (p<0.001). Very low Luciferase activity wasdetected in other tissues of mice injected with Ad5PPE-1-3×Luc.Calculating the Luciferase expression in the lungs as percentage fromthe liver of each injected animal revealed that the activity increased10 fold in the metastatic lung compared to the activity in normal lung(FIG. 49).

In order to localize reporter gene expression to specific cell types,GFP constructs were employed. FIG. 50 A-B show the GFP expression (FIG.50A) in metastatic lungs of Ad5PPE-1-3×GFP injected mice. Immunostainingby CD31 antibody (FIG. 50B) confirm the location of the GFP expressionin the new blood vessels. No GFP expression was detected incontrol—saline injected mice. Low level expression around the epithelialbronchi of the CMV injected mice, but not in the angiogenic bloodvessels of the metastatic lung. In summary, these results indicate thatlarge increases in expression level resulted from introduction of a 3×element into Ad5PPE-1 constructs and that this increased expression wasspecific to the angiogenic blood vessels of tumors. Potentially, theobserved effect may be coupled with the hypoxia response describedhereinabove to further boost expression levels of a sequence ofinterest.

Example 21 Further Characterization of the PPE-1 Hypoxia Response

In order to further characterize the effect of hypoxia on the murinePPE-1 promoter activity, bovine aortic endothelial cells (BAEC) weretransfected by a DNA plasmid (pEL8; FIG. 37A). The pEL8 plasmid containsthe murine PPE-1 promoter (1.4 kb) (red), the luciferase gene (1842 bp),the SV40 poly A sites and the first intron of the endothelin-1 gene, alltermed the PPE-1 promoter cassette was digested and extracted by BamHIrestriction enzyme as described in material and methods. Followingtransfection, cells were subjected to hypoxic conditions.

Luciferase expression in transfected BAEC subjected to 18 hours ofhypoxia (0.5% O2) was eight times higher than Luciferase expression incells grown in a normoxic environment (FIG. 32). FIG. 32 shows thatLuciferase activity (light units/μg protein) in BAEC transfected by aplasmid containing the murine PPE-1 promoter was significantly higherwhen transfected cells were incubated in a hypoxic environment.Equivalent transfection efficiencies were confirmed by co-transfectionwith a β-galactosidase reporter vector and assays of LacZ activity.

In order to determine whether murine PPE-1 promoter delivered byadenoviral vector is also up-regulated by hypoxia, BAEC were transducedby Ad5PPE-1Luc. Ad5CMVLuc was used a non specific control in thisexperiment. Results are summarized in FIG. 33. Hypoxia Luciferaseactivity in BAEC transduced by Ad5PPE-1Luc. In stark contrast, nosignificant difference between normoxia and hypoxia was detected in theAd5CMV transduced cells (FIG. 33).

To understand whether the enhancement of the PPE-1 promoter activity isspecific to endothelial cells, different cell lines (BAEC, B2B, CHO, RINand Cardiac Myocytes) were transduced by Ad5PPE-1 (moi=10) and weresubjected to hypoxia (0.5% O2) or normoxia environment. Results aresummarized in FIG. 34. Luciferase expression was slightly increased inB2B cells and significantly increased in BAEC cells cultured in ahypoxic environment. Luciferase expression in other cell lines wasreduced by the hypoxic environment, compared to normoxia. These resultsconfirm that hypoxic induction of the PPE-1 promoter occurs primarily inendothelial cell lineages.

Example 22 Effect of the 3× Sequence on the PPE-1 Hypoxia Response

In order to ascertain the effect of the 3× sequence on the PPE-1 hypoxiaresponse, BAEC were transduced by Ad5PPE-1Luc and Ad5PPE-1(3×)Luc.Following transduction, the BAEC cells were incubated either in ahypoxic or a normoxic environment as detailed hereinabove. Results aresummarized in FIG. 35. Luciferase expression using the Ad5PPE-1Lucconstruct significantly increased (seven folds) in response to hypoxia(2578 in hypoxia and 322.1 in normoxia). In contrast, theAd5PPE-1(3×)Luc construct exhibited only 1.5 fold increase in responseto hypoxia (from 2874.5 in normoxia to 4315 in hypoxia conditions).These results indicate that the high normoxic level of expressionobserved when the 3× sequence is added to the PPE-1 promoter serves tomask the hypoxic response to some extent.

Example 23 Assays of the PPE-1 Response to Hypoxia in a Transgenic MouseModel

In order to examine the murine PPE-1 promoter activity in tissuessubjected to regional hypoxia/ischemia, mPPE-1-Luc transgenic mice,described hereinabove in materials and methods, were employed. The micewere induced to regional hind limb ischemia as previously described(Couffinhal T. et al. (1998) Am. J. Pathol. 152; 1667-1679). In brief,animals were anesthetized with pentobarbital sodium (40 mg/kg, IP).Unilateral ischemia of the hind limb was induced by ligation of theright femoral artery, approx. 2 mm proximal to the bifurcation of thesaphenous and popliteal to arteries. To verify the induction offunctional change in perfusion, ultrasonic imaging was performed on days4 and 14 by Synergy ultrasound system (GE) equipped with a 7.5 MHztransducer and angiographic software. Animals were housed underconventional conditions for up to 18 days.

Luciferase expression was assayed 2, 5, 10 and 18 days post ligation inthe ischemic muscle, in the normal non-ligated muscle, in the liver,lung, and aorta.

Results, summarized in FIG. 36, show that while no significantdifference was detected in the liver, lung and aorta during the dayspost ligation, Luciferase gene expression increased following thefemoral ligation in both in the normal non-ligated and in the ischemicmuscle. While peak Luciferase expression in the ischemic muscle wasdetected five days post ligation, peak Luciferase expression in thenon-ligated muscle was detected ten days post femoral artery ligation.This indicates that the hypoxic response of the PPE-1 promoter isfunctional in an in-vivo system. Luciferase expression in thenon-ischemic muscle did not change during the days tested, compared toits expression in the control non-operated tissue (day=0). In contrast,Luciferase expression in the ischemic muscle was significantly higher onday 5 than at other time points.

On day 5, PPE-1 driven expression of Luciferase was 2.5 times higherthan in control non-operated mice and compared to the ischemic muscle indays 10 and 18 (FIG. 51).

Expression of Luciferase in other non-ischemic tissues including liver,lungs and aorta of the transgenic mice subjected to regional ischemiarevealed no significant changes within 18 days post ischemic inductionin the Luciferase expression in these tissues (FIG. 52).

Further, these results confirm that Luciferase expression was higher intissues containing a high percentage of endothelial tissue (lung andaorta) than in those tissues containing a low percentage of endothelialtissue (liver and non-ischemic muscle).

Example 24 Effect of Level of Cellular Proliferation on Ad5PPE-1LucActivity in Endothelial Cells

In order to ascertain the effect of level of cellular proliferation onefficiency and specific activity of Ad5PPE-1Luc, an angiogenic model ofendothelial cells (BAEC), was tested in-vitro. Transduced BAEC wereeither induced to quiescence by serum deprivation or grown in 10% FCSfor normal proliferation. Briefly, cells were transduced for 48 hourseither as quiescent cells—72 hours post serum deprivation or asproliferating cells—in normal media (10% FCS). Luciferase activity isexpressed as light unit/μg protein, to normalize for the difference incell amount. The results presented are an average of triplicate testfrom four representative independent experiments.

Luciferase expression under the control of PPE-1 promoter (open bars;FIG. 28) was 4 times higher in normal proliferating BAEC than inquiescent cells, and 25 times higher in normal proliferating BAEC thanLuciferase expression under control of the CMV promoter (Black bars;FIG. 28). Further, in proliferating cells, the activity under thecontrol of PPE-1 promoter was 10 times higher than that under the CMVpromoter control.

In order to simulate angiogenic conditions in-vitro, Ad5PPE-1Lucactivity was tested in BAEC induced to rapid proliferation by additionof 40 ng/ml vascular endothelial growth factor (VEGF). Activity underthese conditions was compared activity in normal proliferating cells andquiescent cells as described hereinabove. Luciferase expression in BAECinduced to cell proliferation with VEGF was 44 times higher than innormal proliferating cells, and 83 times higher than in quiescent cells(FIG. 40).

Together, these experiments indicate that the level of activity of asequence of interest under transcriptional control of the PPE-1 Promoteris a function of the level of cellular proliferation, with rapidproliferation causing higher levels of expression.

Example 25 Assays of the PPE-1 Promoter in Atherosclerosis Induced Mice

In order to test the efficiency and specificity of the Ad5PPE-1 vectorin atherosclerotic blood vessels, 10¹⁰ pfu/ml of the viral vectors weresystemically injected to 6 month old ApoE deficient mice (Plump, A. S.et al. Cell; 1991; 71:343-353).

As ApoE deficient mice age, they develop high cholesterol values andextensive atherogenic plaques with no induction of lipid reach diet.FIG. 43 is a picture of an aorta dissected from an ApoE deficient mousecolored by Sudan—IV. Note that the thoracic aorta contains less redstained atherosclerotic lesions while the abdominal region is highlyatherosclerotic. (FIG. 43 adapted from Imaging of Aortic atheroscleroticlesions by 125I-HDL and 125I-BSA. A. Shaish et al,Pathobiology—Pathobiol 2001; 69:225-9).

FIG. 44 summarizes Luciferase expression observed 5 days post systemicinjections of Ad5PPE-1Luc (open bars; n=12) and Ad5CMVLuc (black bars;n=12) to ApoE deficient mice. Results are presented as absoluteLuciferase expression in the thoracic area that contains lessatherosclerotic lesion, and the abdominal aorta that is richatherosclerotic lesion.

Luciferase expression controlled by the PPE-1 promoter was 6 fold higherin the highly atherosclerotic abdominal, and 1.6 fold higher in theslightly atherosclerotic thoracic aorta as compared to expression underthe control CMV promoter.

No significant difference was observed between the two aorta regions inthe Ad5PPE-1Luc injected mice, while higher Luciferase expression wasobserved in thoracic aorta of the Ad5CMVLuc injected group compared tolow expression in the abdominal aorta that contain lesion.

These results indicate that while a constitutive promoter (CMV) has atendency to shut down in areas where atherosclerosis is most severe, thePPE-1 promoter is relatively unaffected by disease progression.

Example 26 Assays of the PPE-1 Promoter in a Wound Healing Model

In order to test the Ad5PPE-1 constructs efficiency and specificactivity in directing Luciferase expression to healing wound bloodvessels, a murine wound healing as described hereinabove in Material andMethods was employed.

As in other experiments, Ad5CMVLuc was used as a non-tissue specificcontrol. Luciferase activity under the PPE-1 promoter (FIG. 45; openbars) control was higher both in the normal (6.8±3.2) and in healingwound region (5±1.6) compared to the activity observed under the CMVcontrol (FIG. 45; black bars).

Because both the CMV and PPE-1 promoter exhibited reduced expressionlevels in the healing wound, these results are difficult to interpret.Despite this unexpected observation, it is clear that the PPE-1 promoterdrives higher levels of expression than the CMV promoter in both normaland healing tissue. The presence of necrotic scar tissue may account forthe reduced expression levels observed with both promoters in thehealing wound.

Example 27 Targeted Expression of VEGF and PDGF-B to Ischemic MuscleVessels

In-vivo induction of angiogenesis oftentimes results in a primitivevessel network consisting of endothelial cells. These nascent vesselsrupture easily, prone to regression and leakiness and poorly perfused.To overcome these limitations localized, timed and dose-controlleddelivery of various angiogenic factors, capable of recruitingendothelial cells as well as periendothelial cells (i.e., pericytes insmall vessels or smooth muscle cells in larger vessels) is desired.

The modified preproendothelin-1 promoter, PPE-1-3× was used to expressin the endothelium of ischemic limb muscles either VEGF or PDGF-B, anendothelial secreted factor which recruits smooth muscle cells towardsthe origin of secretion thereby preventing hyper permeability of newlyformed vessels.

To determine expression of VEGF and PDGF-B in ischemic tissues, in-situhybridization was performed. As shown in FIGS. 54A-C, while asignificant expression of VEGF mRNA could be detected in ischemic musclesections from Ad5PPE-1-3×VEGF treated mice, essentially no signal couldbe seen in muscle sections of Ad5CMVVEGF or saline-treated mice.Similarly, the presence of mRNA of PDGF-B was detected in ischemic limbmuscles of mice treated with Ad5PPE-1-3×PDGF-B, but not in Ad5CMVPDGF-Bor saline-treated mice (FIGS. 54E-G). Interestingly, the pattern of thesignal in FIGS. 12A and 12E resembled vascular structure. Notably,representative liver sections from the various treatment groupsdemonstrated massive expression of VEGF or PDGF-B in Ad5CMV treatedanimals (FIGS. 54D and 54H), while no expression was detected in thelivers of Ad5PPE-1-3× vectors treated mice (data not shown).

Altogether, the assay indicates that the Ad5PPE-1-3× vectors mediatemeasurable expression of angiogenic factors in a target organ, while theconstitutive Ad5CMV vectors expressed their transgene almost exclusivelyin hepatic tissues.

Example 28 Enhanced Angiogenesis by PPE-Mediated VEGF Expression

The therapeutic effect of Ad5PPE-1-3×VEGF was compared to that ofpreviously reported Ad5CMVVEGF. 10⁹ PFUs of either therapeutic vectors,as well as reporter vector Ad5CMV luciferase and equivalent volume ofsaline as control were systemically administered to mice, 5 daysfollowing femoral artery ligation. Ultrasonic (US) images of the medialaspect of both limbs were taken in angiographic mode. As shown in FIGS.38A-D, 21 days following ligation, the signal of perfusion wasdiminished and truncated in the control animals; however, continuous,enhanced signal was seen in the US images of both Ad5PPE-1-3×VEGF andAd5CMVVEGF treated mice. The mean intensity of perfusion on the 21^(st)day in the two VEGF treatment groups was over 3 times higher than thatof the control group (p<0.01), and similar to that recorded from thenormal, contralateral limbs of the animals (FIG. 38E).Immunohistochemistry analysis done 21 days following femoral arteryligation and using anti CD-31, an endothelial specific marker, showed amean of 546 CD31+ cells/mm² in the ischemic muscle sections ofAd5PPE-1-3×VEGF treated mice, comparing to 585 and 485 CD31+ cells/mm²in the Ad5CMVVEGF and control groups, respectively (FIG. 38F). This datashows that in the short term treatment with Ad5PPE-1-3×VEGF is aseffective as the treatment with the potent CMV promoter of Ad5CMVVEGF.Furthermore, liver sections of the mice stained in H&E showed noindications for hepatitis or other pathological chronic changes (datanot shown), thereby ruling out adenovirus tropic effect on hepatocytes

Example 29 Prolonged Effect of VEGF Gene Therapy by PPE-RegulatedExpression

Tissue specific expression versus constitutive expression ofpro-angiogenic factors was addressed with respect to the induction ofangiogenesis. The effects of PPE-regulated and CMV-regulated VEGFexpression on perfusion and angiogenesis were tested in 70 days longexperiments. Mice with ischemic limb were treated as above (see Example28). US imaging revealed significant improvement in perfusion in bothtreatment groups beginning 1-2 weeks following virus administration,while minor changes were detected in the control group (data not shown).The long-term effect of the Ad5PPE-1-3×VEGF treatment was detected 50and 60 days following femoral artery ligation. Perfusion wassignificantly increased in the Ad5PPE-1-3×VEGF treated mice, as comparedto Ad5CMVVEGF or saline-treated mice. The difference in perfusionbetween Ad5CMVVEGF and control treated animals decreased over that timeinterval. On the 50^(th) day, mean intensity of perfusion in theAd5PPE-1-3×VEGF treated group was about 50% higher than in theAd5CMVVEGF or saline treated mice, and similar to that of thecontralateral normal limb (p<0.01, FIG. 55A). Upon sacrifice of theanimals on the 70^(th) day, the capillary density in the muscle sectionsof Ad5PPE-1-3×VEGF treated mice was 747 CD31+ cells/mm², which is 57%and 117% higher than in the Ad5CMVVEGF (474 CD31+ cells/mm²) and control(342 CD31+ cells/mm²) groups, respectively (p<0.01, FIG. 55B).

Example 30 Enhanced Angiogenesis by PPE-Promoter Endothelial-SpecificPDGF-B Expression

PDGF-B is a paracrine endothelial secreted factor, which has been shownto be involved in vessel maturation by recruitment of smooth musclecells, and probably also in angiogenesis [Edelberg, J. M. et al.Circulation 105, 608-13. (2002); Hsu et al. J Cell Physiol 165, 239-45.(1995); Koyama, N. et al. J Cell Physiol 158, 1-6. (1994)]. It has alsobeen shown that PDGF-B is involved in intimal thickening [Sano, H. etal. Circulation 103, 2955-60. (2001); Kaiser, M., et al. Arthritis Rheum41, 623-33. (1998)] and in fibroblast proliferation [Nesbit, M. et al.Lab Invest 81, 1263-74. (2001); Kim, W. J. et al. Invest Ophthalmol VisSci 40, 1364-72. (1999).]. The ability of PDGF-B to induce angiogenesisunder endothelial specific regulation was tested in vitro and in-vivo.

Ad5PPE-1-3×PDGF-B vector induced angiogenic changes in endothelial cellsin-vitro, like Ad5PPE-1-3×VEGF (data not shown). Transduction ofendothelial cells cultured on fibrin coated cultureware with 10 MOI ofAd5PPE-1-3×PDGF-B resulted in the formation of 2-dimensional circularstructures and fibrin degradation.

For in-vivo effect, mice were systemically treated with 10⁹ PFUs ofAd5PPE-1-3×PDGF-B, 5 days following femoral artery ligation. 30 daysfollowing ligation the mean intensity of perfusion in theAd5PPE-1-3×PDGF-B treated mice was about 90% higher than that in thecontrol group (FIG. 56A). 80 days following ligation the intensity ofperfusion in the Ad5PPE-1-3×PDGF-B treated group was 60% higher than inthe control group (FIG. 56B)

Capillary density was measured 35 and 90 days following ligation. In theshort time interval, the mean capillary density in ischemic musclesections of the Ad5PPE-1-3×PDGF-B treated mice was 516 CD31+ cells/mm²,while in the saline-treated group it was 439 (FIG. 56C). 90 daysfollowing ligation the mean capillary density in Ad5PPE-1-3×PDGF-Btreated mice increased slightly to 566 CD31+ cells/mm², while a moderatedecrease was detected in the control group (378 CD31+ cells/mm², FIG.56D)

The results indicate that Ad5PPE-1-3×PDGF-B vector by itself is a potentangiogenic treatment, which not only induces angiogenesis in the shortterm following administration, but is capable of retaining a therapeuticeffect for a long period of time. No chronic changes were detected inthe livers of the mice treated with Ad5PPE-1-3×PDGF-B.

Example 31 Vessel Maturation by PDGF-B Expression in Endothelial Cells

The assumption that further enhancement of angiogenesis and maturationof vasculature can be achieved by utilizing both VEGF and PDGF-B in acombination therapy was tested using two modalities of treatment: (i)single administration of 10⁹ PFUs of Ad5PPE-1-3×VEGF and ofAd5PPE-1-3×PDGF-B; (ii) administration of similar dose ofAd5PPE-1-3×PDGF-B 5 days following administration of Ad5PPE-1-3×VEGF.Both modalities yielded the same results, and therefore are referred toas one. 90 days following ligation, both the combination therapy and theAd5PPE-1-3×VEGF treated mice exhibited significantly higher capillarydensity as compared to the control, Ad5PPE-1-3×GFP treated mice, butthere was no significant difference among the various therapeutic groups(FIG. 57B). However, the mean intensity of perfusion in US imaging inthe combination therapy group was up to 42% higher than theAd5PPE-1-3×VEGF treated group (FIG. 57A). This can be explained bymaturation of small vessels in the ischemic muscles of the combinationtherapy groups and Ad5PPE-1-3×PDGF-B treated mice. Significant stainingfor vascular smooth muscle cells was seen in muscle sections from micetreated with the combination therapy or Ad5PPE-1-3×PDGF-B, immunostainedfor α-SMactin (FIGS. 57C-D). Sparse staining could be seen in controland Ad5PPE-1-3×VEGF treated mice (FIGS. 57E-F). In the normal limbmuscles there was prominent staining around larger arterioles andvenules (FIG. 57G). Similar results were obtained as early as 35 daysfollowing ligation in mice treated with Ad5PPE-1-3×PDGF-B (data notshown). No chronic changes were apparent in liver sections of treatedmice 35 days following ligation.

These results were further substantiated in a separate experiment, whichaddressed the effect of PDGF-B alone and in combination therapy on bloodperfusion 50 days following ligation. As shown in FIG. 58, 50 daysfollowing ligation, blood perfusion intensity in the combination therapygroup resembled completely that of normal limb. This effect was PPE-3×dependent, as constitutive expression (CMV promoter) of both growthfactors resulted in only half perfusion capacity. Interestingly, PPE-3×dependent expression of PDGF-B alone could mediate nearly the sameperfusion (i.e., 77%) as induced by the combination therapy. However,such results were not apparent using a constitutive promoter.

These results corroborate that the PPE-1-3× promoter is capable ofstrong enough activation of the therapeutic genes, in spite of thesystemic administration, without compromising the preferentialexpression in angiogenic endothelial cells. Furthermore, these resultssubstantiate PDGF-B as a pro-angiogenic factor which can mediate itsangiogenic action without further addition of well establishedangiogenic growth factors, such as VEGF.

Example 32 Construction and Characterization of the AdPPE-1(3×)-TKVector

The HSV-TK/GCV is the most widely studied and implemented cytoreductivegene-drug combination. Cells transfected with an HSV-TK-containingplasmid or transduced with an HSV-TK containing vector, are madesensitive to the drug super-family including aciclovir, ganciclovir(GCV), valciclovir and famciclovir. The guanosine analog GCV is the mostactive drug in combination with TK. HSV-TK positive cells produce aviral TK, which is three orders of magnitude more efficient inphosphorylating GCV into GCV monophosphate (GCV-MP) than the human TK.GCV-MP is subsequently phosphorylated by the native thymidine kinaseinto GCV diphosphate and finally to GCV triphosphate (GCV-TP).

Initially, two plasmids were prepared. One plasmid contains the HSV-TKgene controlled by the modified murine pre proendothelin-1 (PPE-13×)promoter and was prepared in order to test the efficacy of the genecontrolled by the PPE-1(3×) promoter in vitro. A larger plasmidcontaining the HSV-TK (gene controlled by the PPE-1(3×) promoter as wellas adenoviral sequences was prepared for virus vector preparation byhomologous recombination. The HSV-TK gene (1190 bp) was digested fromthe 4348 bp plasmid pORF-HSV1TK by two restriction enzymes. The SalIrestriction site was positioned against the 5′ end of the HSV-TK geneand the EcoRI site was positioned against the 3′ end. The HSV-TK genewas ligated to the multiple cloning site of the 3400 bp plasmidpBluescript-SK that contains a Nod restriction site upstream to theinserted gene (against the 3′ end of the HSV-TK gene). The SalI siteunderwent the Klenow procedure and the Nod linker was ligated to the 5′end of the HSV-TK gene. The HSV-TK gene (now outflanked by two Nodrestriction sites) was ligated into the NotI restriction site of twoplasmids, pEL8(3×)-Luc and pACPPE-1(3×)-GFP, described hereinabove:

1. The 8600 bp plasmid designated pEL8(3×)-Luc, instead of the 1842 bpluciferase gene, flanked by two Nod restriction sites. The pEL8(3×)-TKplasmid contains the PPE-1(3×) promoter, the HSV-TK gene, an SV-40poly-adenylation site and the first intron of the murine endothelin-1gene (FIG. 60 a).

2. The 11946 bp plasmid pACPPE-1(3×)-GFP instead of the 1242 bp greenfluorescent protein (GFP) gene, outflanked by two Nod restriction sites(FIG. 60 b).

Constructing an Adenovirus-5 Vector Armed with the HSV-TK GeneControlled by the Modified Murine Pre-Proendothelin-1 Promoter.

The replication-deficient vector, designated AdPPE-1(3×)-TK, wasconstructed on the basis of a first generation (E1 gene deleted, E3incomplete) adenovirus-5 vector. The recombinant vector was prepared byco-transfection of the plasmids pACPPE-1(3×)-TK and pJM-17 (40.3 kb) inhuman embryonal kidney-293 (HEK-293) using well-known conventionalcloning techniques. The pJM-17 plasmid contains the entire adenovirus-5genome except for the E1 gene. The HEK-293 cell line substitutes the E1deletions, since they contain an E1 gene in trans. One out of 40homologous recombinations induced the vector AdPPE-1(3×)-TK.

AdPPE-1(3×)-TK Vector Characterization.

PCR analysis was performed on the viral DNA in order to verify theexistence of the TK transgene and the promoter in the recombinantadenovirus. Two primers were used: the forward primer5′-ctcttgattcttgaactctg-3′ (455-474 bp in the pre-proendothelin promotersequence) (SEQ ID No: 9) and the reverse primer5′-taaggcatgcccattgttat-3′ (1065-1084 bp in the HSV-TK gene sequence)(SEQ ID No:10). Other primers of vectors, produced in our laboratories,were used in order to verify the purity of the vector. A band ofapproximately 1 kb verified the presence of the PPE-1(3×) promoter andthe HSV-TK gene in the AdPPE-1(3×)-TK virus (FIG. 61). However, none ofthe other primers of the adenovirus vectors constructed afforded anyproduct. Thus, the vector was a pure colony.

The virus was further purified in HEK-293 cells in order to isolate asingle viral clone.

Viral DNA of AdPPE-1(3×)-TK was sequenced by cycle sequencing reactionsin the presence of a dideoxy nucleotides, chemically modified tofluoresce under UV light. Four primers were used to verify the existenceof the whole transgene:

1. Forward primer 5′-ctcttgattcttgaactctg-3′ (455-474 bp in thepre-proendothelin promoter) (SEQ ID NO: 9) preceding the “3×” element.

2. Reverse primer 5′-gcagggctaagaaaaagaaa-3′ (551-570 bp in thepre-proendothelin promoter) (SEQ ID NO: 11).

3. Forward primer 5′-tttctttttcttagccctgc-3′ (551-570 bp in thepre-proendothelin promoter) (SEQ ID NO:12).

4. Reverse primer 5′-taaggcatgcccattgttat-3′ (1065-1084 bp in the HSV-TKgene) (SEQ ID NO:10) within the HSV-TK gene.

The primers designated 2 (SEQ ID NO:11) and 3 (SEQ NO:12) were used,since no product was obtained by the primers 1 (SEQ ID NO:9) and 3 (SEQID NO:10) alone. The result exhibited 99% identity to the Mus musculusBalb/c pre-proendothelin-1 gene, promoter region gi|560542|gb|U07982.1|MMU07982[560542] (SEQ ID NO:1), as well as 99.4% identity to thethymidine kinase gene of the herpes simplex virus gi|59974|emb|V00470.1|HERPES[59974]. The sequence of AdPPE-1(3×) is detailed in FIG. 92.

The 3× sequence (FIG. 93) contains an additional triplicate repeat ofthe endothelial specific positive transcription elements. In this 145 bpsequence there are two complete endothelial specific positivetranscription elements and one sequence cut into two fragments inopposite order, as described hereinabove.

Control Vectors.

Two adenovirus vectors, one lacking the PPE-1(3×) promoter, and a secondlacking the Luc gene, were constructed to serve as controls for theAdPPE-1(3×) vector. The vector AdCMV-TK (used as a non tissue-specificpromoter control) contains the HSV-TK gene controlled by the earlycytomegalovirus (CMV) promoter (FIG. 62 c. The vector AdPPE-1(3×)-Luccontains the luciferase (Luc) gene controlled by the modified murinepre-proendothelin-1 promoter (FIG. 62 b). The viruses were grown inscaled up batches and stored at −20° C. at a concentration of 10⁹-10¹²particles/ml.

Example 33 Cytotoxicity of Ganciclovir and TK Under Control of the PPE-1(3×) Promoter Superior Endothelial Cell Cytotoxicity of TK Under Controlof the PPE-1 (3×) Promoter In-Vitro

Specific endothelial cell-targeted cytotoxicity of AdPPE-1(3×)-TK wasassessed in-vitro in endothelial cell lines by comparison to controlvectors AdCMV-TK and AdPPE-1(3×)-Luc.

AdPPE-1(3×)-TK+GCV is Cytotoxic at Low Multiplicity of Infection (MOI):

Bovine aorta endothelial cells (BAECs) were transduced withAdPPE-1(3×)-TK, AdCMV-TK and AdPPE-1(3×)-Luc multiplicity of infections(m.o.i.) of 0.1, 1, 10, 100, and 1000. GCV (1 μg/ml) was added fourhours post-transduction. Controls were cells transduced with the vectorswithout GCV, or GCV without vectors. Both controls did not induce celldeath (data not shown). Note the morphological changes characteristic tocytotoxicity (cell enlargement, elongation and bloatedness) and loss ofconfluence evident in AdPPE-1 (3×)+GCV-treated cells, at a significantlylower m.o.i. than AdCMV-TK. Cells transduced with AdPPE-1 (3×)-Lucremained healthy (small size, rounded and confluent, FIG. 63).Assessment of cell viability, determined by staining with crystal violet(FIG. 64), confirmed that the AdPPE-1(3×)-TK vector, combined with GCVadministration, exhibited greater cytotoxicity, at lower m.o.i. in BAEcells than the TK gene controlled by the strong constitutive CMVpromoter.

AdPPE-1(3×)-TK+GCV is Cytotoxic at Low Concentrations of GCV:

Bovine aorta endothelial cells (BAECs) were transduced withAdPPE-1(3×)-TK, AdCMV-TK and AdPPE-1(3×)-Luc, as described hereinabove,at multiplicity of infection (m.o.i) of 10, and exposed to increasingconcentrations of GCV (0.001-10 μg/ml, as indicated), added four hourspost-transduction. Control cells transduced with the vectors withoutGCV, or receiving GCV without vectors show no indication of cell death(data not shown) at any concentrations. Note the morphological changescharacteristic to cytotoxicity (cell enlargement, elongation andbloatedness) and loss of confluence evident in AdPPE-1(3×)-TX+GCV-treated cells (FIG. 65), at a significantly lowerconcentration of GCV than cells exposed to AdCMV-TK (middle series).Assessment of cell viability, determined by staining with crystal violet(FIG. 66), confirmed that the AdPPE-1(3×)-TK vector, combined with GCVadministration, exhibited greater cytotoxicity in BAE cells, and atlower GCV concentrations than the TK gene controlled by the strongconstitutive CMV promoter.

AdPPE-1(3×)-TK+GCV Cytotoxicity is Specific for Endothelial Cells:

In order to evaluate the specificity and the efficacy of the vectorAdPPE-1(3×)-TK for endothelial cells, endothelial [Bovine aorticendothelial cells (BAEC), Human umbilical vein endothelial cells(HUVEC)] and non-endothelial [Human hepatoma cells (HepG-2), Humannormal skin fibroblasts (NSF)] cells were transduced withAdPPE-1(3×)-TK, AdPPE-1(3×)-Luc or AdCMV-TK at m.o.i. of 10, followed bythe administration of 1 μg/ml GCV four hours post-transduction.Cytotoxicity and cell morphological changes were detected four dayspost-transduction. AdPPE-1(3×)-TK+GCV induced cytotoxicity, specificallyin BAEC and HUVEC, while AdCMV-TK+GCV induced cytotoxicity only inHepG-2. NSF were resistant to all vectors at m.o.i.=10.AdPPE-1(3×)-Luc+GCV were nontoxic to all cell types (FIG. 67).Assessment of cell viability, determined by staining with crystal violet(FIG. 68), confirmed that the AdPPE-1(3×)-TK vector, combined with GCVadministration, exhibited synergic endothelial cell-specificcytotoxicity, compared to the non-specific cytotoxicity of the TK genecontrolled by the strong constitutive CMV promoter (AdCMV-TK+GCV).

When non-endothelial NSF cells were transduced with AdPPE-1(3×)-TK,AdPPE-1(3×)-Luc or AdCMV-TK, at the higher m.o.i. of 100, followed bythe administration of 1 μg/ml GCV four hours post-transduction, noeffect of AdPPE-1(3×)-TK+GCV on cell morphology was observed (FIG. 69).In contrast, cells treated with TK under control of the strongconstitutive CMV promoter (AdCMV-TK+GCV) showed strong non-specificcytotoxicity, confirming the endothelial selective cytotoxicity of TKunder control of the PPE-1 (3×) promoter and ganciclovir administration,even at extreme multiplicity of infection.

Taken together, these results show, for the first time, that the vectorAdPPE-1(3×)-TK is able to specifically induce the killing of endothelialcells, including human endothelial cells. Moreover, the vectorAdPPE-1(3×)-TK is fully controlled by the prodrug GCV and is quiteactive at relatively low GCV concentrations. Finally, although theendothelial cell transduction efficacy of the adenovirus vector isrelatively low, endothelial cell killing is highly effective.

Example 34 Therapeutic Effect of Administration of Ganciclovir and TKUnder Control of the PPE-1 (3×) Promoter Superior Endothelial CellCytotoxicity of TK Under Control of the PPE-1 (3×) Promoter In-Vivo

The therapeutic efficacy of the specific endothelial cell-targetedcytotoxicity of AdPPE-1(3×)-TK was assessed in-vivo by comparison tosystemic administration of GCV and control vectors AdCMV-TK andAdPPE-1(3×)-Luc, in animal models of cancer tumorigenesis and metastaticgrowth.

Synergic Suppression of Metastatic Growth in Lewis Lung Carcinoma (LLC)by In Vivo Expression of TK Under Control of the PPE-1 (3×) Promoter andGanciclovir (GCV) Administration:

Lewis Lung Carcinoma is a well-characterized animal model of severelyaggressive, malignant cancer with high metastatic potential. Combinationtherapy with HSV-TK has been attempted using cytokine IL-2 (Kwong et al,Chest 119; 112:1332-37), with the endothelial promoter Tie/Tek and GCV(dePalma et al, Nat Med 2003; 9:789-795) and with the VEGF promoter andGCV in-vitro (Koshikowa et al Canc Res 2000; 60:2936-41). In order totest the effect of systemic administration of AdPPE-1(3×) and GCV onmetastatic disease, LLC lung metastases were induced by the inoculationof the left foot with tumor cells and foot amputation as soon as theprimary tumor developed. Adenovirus vectors [AdPPE-1(3×)-TK+GCV;AdCMV-TK+GCV; AdPPE-1(3×)-TK without GCV] were administeredintravenously five days post primary tumor removal, followed by dailyintraperitoneal GCV administration for 14 days.

Mice exclusion was as follows: 22 mice were excluded since no primarytumor developed, one mouse was excluded due to vector injection failure,8 mice died without any traces of lung metastasis. Of the excluded mice,18 mice were excluded before enrollment, 6 were excluded from group1(AdPPE-1(3×)-TK+GCV), 2 from group 2(AdCMV-TK+GCV), 3 from group3(AdPPE-1(3×)-TK without GCV) and 2 from group 4 (Saline+GCV). The micewere sacrificed on the 24^(th) day post vector injection. On that day2.5% of the mice in the control groups (saline+GCV and AdPPE-1(3×)-TKwithout GCV) had died from the spread of lung metastases. FIG. 70 showsrepresentative lung tissue from treated and control groups, showing thesignificantly reduced extent of metastatic spread in the lungs ofAdPPE-1 (3×)-TK+GCV treated mice, compared to those from mice treatedwith AdCMV-TK+GCV, AdPPE-1(3×)-TK without GCV and GCV withoutadenovirus.

Upon sacrifice, the mean weight (an indication of extent of metastaticdisease) of the metastases of mice treated with AdPPE-1(3×)-TK+GCV was3.3 times lower than that of mice treated with AdPPE-1(3×)-TK withoutGCV (mean±SE: 0.3 g±0.04 vs. 0.8 g±0.2, respectively; p<0.05). The meanweight of the metastases of mice treated with AdCMV-TK+GCV or withsaline+GCV was not statistically different from that of the other groups(FIG. 71).

Cytotoxic Effect of In Vivo Expression of TK Under Control of the PPE-1(3×) Promoter and Ganciclovir (GCV) on Metastatic Lung Tissue:

In order to determine the mechanism of the effect of AdPPE-1(3×) and GCVadministration on LLC metastatic growth, hematoxylin and eosin stainingwas performed on lung tissue from metastatic lungs (FIGS. 72 a-72 c).Mild peripheral necrosis was detected in lung metastases taken from micetreated with AdPPE-1(3×)-TK without GCV or saline+GCV (FIG. 72 a). Lungtissue taken from mice treated with AdPPE-1(3×)-TK+GCV demonstratedalveolar and peribronchial mononuclear infiltrates, while no infiltrateswere detected in lungs taken from mice treated with AdPPE-1(3×)-TKwithout GCV or saline+GCV. Lung metastases taken from mice treated withAdPPE-1(3×)-TK GCV demonstrated clusters of mononuclear infiltratescompared to metastases taken from mice treated with AdPPE-1(3×)-TKwithout GCV or saline+GCV (FIG. 72 b,c). Minimal necrosis andmononuclear infiltrates were also detected in specimens taken from micetreated with AdCMV-TK+GCV. The result suggest that AdPPE-1(3×)-TK+GCVinduce increased central necrosis and mononuclear infiltrates in lungmetastases.

To determine the character of cell death responsible for the inhibitoryeffect of AdPPE-1(3×)-TK+GCV on LLC lung metastases, TUNEL andanti-caspase-3 staining were performed on lung tissue for assessment ofapoptosis. Lung metastases from AdPPE-1(3×)-TK+GCV treated micedemonstrated numerous apoptotic tumor cells compared to mice treatedwith AdPPE-1(3×)-TK without GCV or saline+GCV (FIGS. 73 a and 73 h).Histopathology sections of specimens taken from lungs of mice treatedwith AdPPE-1(3×)-TK+GCV demonstrated a significantly higher extent ofboth DNA damage (TUNEL, FIG. 73 a) and caspase-3 (FIG. 73 b), indicatingtumor cell apoptosis, than specimens from mice treated withAdCMV-TK+GCV. More significantly, TUNEL and caspase-3 staining ofhistopathology sections from the metastatic lungs exhibited enhancedapoptosis in the vascular (endothelial) regions of the lung metastasesfrom the mice treated with intravenous AdPPE-1 (3×)-TK+GCV (FIG. 74),indicating synergic enhancement of metastatic cell apoptosis by in vivoexpression of TK under control of the PPE-1 (3×) promoter andganciclovir (GCV) administration. The results suggest that systemicadministration of AdPPE-1(3×)-TK+GCV induces massive tumor cellapoptosis. Moreover, angiogenic endothelial cell apoptosis may be themechanism for massive central metastatic necrosis and apoptosis.

Expression of TK Under Control of the PPE-1 (3×) Promoter andGanciclovir (GCV) Administration have Anti-Angiogenic Effects inMetastatic Disease In-Vivo:

CD-31 is a characteristic endothelial cell marker of angiogenesis. AntiCD-31 staining was performed on metastatic lung tissue in order todetermine the involvement of endothelial cells in the anti-metastaticeffects of systemic AdPPE-1(3×)+GCV. FIGS. 75 a-75 d reveal thatangiogenic vessels in lung metastases from AdPPE-1(3×)-TK+GCV treatedmice were short, without continuity or branching and with indistinctborders (FIGS. 75 a-75 c). Angiogenic blood vessels in lung metastasesfrom mice treated with AdPPE-1(3×)-TK without GCV or saline+GCVdemonstrated long blood vessels with abundant branching and distinctborders (FIG. 75 a). Minimally abnormal vasculature was also detected inlung metastases of AdCMV-TK+GCV treated mice, although much smaller thanthose of mice treated with AdPPE-1(3×)-TK (not shown). The specificityof this anti-angiogenic effect for proliferating endothelial tissue isshown by the absence of effect on hepatic blood vessels (FIG. 75 c).Computer based vascular density measurement (Image Pro-Plus, MediaCybernetics Incorporated), demonstrated 1.5 times smaller vasculardensity in lung metastases of the AdPPE-1(3×)-TK+GCV group than in thegroup treated with AdPPE-1(3×)-TK without GCV (40107.7 μm² versus61622.6 mm², respectively) (FIG. 75 d).

Taken together, these results indicate that systemic administration ofAdPPE-1(3×)-TK+GCV induces central metastatic necrosis and apoptosis viahighly selective induction of angiogenic endothelial cell apoptosis.

Systemic AdCMV-TK+GCV Administration Induces Hepatotoxicity in MiceBearing LLC Lung Metastases.

Since one of the major side effects of systemic administration ofadenovirus vectors is liver toxicity, liver morphology was assayed inC57Bl/6 mice with induced LLC tumors. Analysis of hematoxylin and eosinstained sections of treated and control liver tissues revealed thatlivers from treated mice treated with TK under control of theconstitutive promoter AdCMV-TK+GCV exhibited portal and periportalmononuclear infiltrates and small confluent necrotic areas, whereaslivers from mice treated with AdPPE-1(3×)-TK+GCV, and control groups,exhibited only minimal mononuclear infiltrates and hepatocyte nuclearenlargement (FIG. 76). The results demonstrate that while constitutiveexpression of TK under control of the CMV promoter is clearlyhepatotoxic, no adverse side effects on liver morphology were observedwith the angiogenesis-specific AdPPE-1(3×)-TK+GCV treatment.

Strict Organ Specificity of Expression of TK Under Control of the PPE-1(3×) Promoter In-Vivo:

In order to assess the extent of organ- and tissue specificity of theanti-metastatic effects HSV-TK expression under control of the PPE-1(3×)promoter, PCR analysis using HSV-TK and β-actin primers was performed ona variety of tissues from different organs of mice bearing LLC lungmetastases treated with adenovirus vectors.

Nine C57BL/6 male mice aged 15 weeks were enrolled. LLC lung metastaseswere induced by inoculation of the left foot with tumor cells and footamputation as soon as the primary tumor developed. Adenovirus vectors(AdPPE-1(3×)-TK and AdCMV-TK) or saline were delivered intravenously 14days post primary tumor removal. The mice were sacrificed 6 days postvector injection and RNA was extracted from the harvested organs, asdescribed. Reverse transcriptase-PCR was performed on RNA followed byPCR using HSV-TK and β-actin primers. Positive HSV-TK expression wasdetected in the lungs of mice treated with AdPPE-1(3×)-TK, while noHSV-TK expression was detected in the liver. In contradistinction,highly positive HSV-TK expression was detected in the livers of micetreated with AdCMV-TK and no expression was detected in the lungs (FIG.77). Computer based densitometry (Optiquant, Packard-Instruments),corrected for β-actin, demonstrated lung/liver expression ratio of 11.3in the AdPPE-1(3×)-TK treated mice, compared with the liver/lungexpression ratio of 5.8 in the AdCMV-TK treated mice. These resultsdemonstrate that the AdPPE-1(3×)-TK treated mice express the HSV-TK genepredominantly in angiogenic-rich organs, i.e. the metastatic lung,whereas expression of TK under control of the CMV promoter (AdCMV-TKtreated mice) was prominent in Coxsackie adenovirus receptor-richorgans, such as the liver (FIG. 77). Strong positive HSV-TK expressionwas also detected in testis of AdPPE-1(3×)-TK treated mice. While notwishing to be limited by a single hypothesis, it will be appreciated tothat the positive expression in the AdPPE-1(3×)-TK treated mouse islikely explained by a high expression of endothelin promoter in thegonads. The positive expression in the AdCMV-TK treated mouse isexplained by the relatively high RNA elution, as mirrored by the highlypositive β-actin band.

Taken together, these results indicate that systemic administration ofAdPPE-1(3×)-TK+GCV can efficiently inhibit even highly aggressivemetastatic spread of cancer in a safe and tissue specific manner, viainduction of central metastatic necrosis and selective induction ofangiogenic endothelial cell apoptosis.

Example 35 Administration of Ganciclovir and TK Under Control of thePPE-1 (3×) Promoter in Combination with Radiotherapy SynergicEndothelial Cell Cytotoxicity In-Vivo

Multiple modality anticancer therapies provide significant advantagesover individual therapies, both in terms of reduction in requireddosages and duration of treatment, leading to a reduction in undesirableside effects, and in terms of greater efficacy of treatment arising fromsynergic convergence of different therapeutic mechanisms (for a recentreview, see Fang et al, Curr Opin Mol Ther 2003; 5:475-82). In order totest the efficacy of AdPPE-1(3×)-TK+GCV administration in multimodalitytherapy, the effect of systemic AdPPE-1(3×)-TK+GCV administration on aslow growing primary CT-26 colon carcinoma in Balb/C mice, andmetastatic Lewis Lung Carcinoma in C57Bl/6 mice, combined withsingle-dose radiotherapy was assessed.

Local Single-Dose 5 Gy Radiotherapy is Non-Toxic and Sub-Therapeutic toBalb/C Mice Bearing a Primary CT-26 Colon Cancer Tumor:

Twenty BALB/C male mice aged 8 weeks were inoculated with CT-26 coloncarcinoma into the left thigh in order to find a radiation dose which isboth sub-therapeutic and non-toxic. As soon as the tumor diameterreached 4-6 mm, the mice were treated with a local single-dose ofradiation. Four radiation doses were examined: 0 (black circles), 5(open circles), 10 (black triangles), or 15 (open triangles) Gy. Tumorvolume [calculated according to the formula V=π/6×α²×β (α is the shortaxis and β is the long axis)] was assessed daily by measuring the largeand small axes. Mouse well-being was monitored daily by observation andweighing. 10 and 15 Gy doses suppressed tumor progression developmentcompared to untreated mice (p=0.039, p=0.029, respectively). However,the 5 Gy dose induced only a partial, non-statistically significantdelay in tumor progression (FIG. 78 a), and no significant weight loss(FIG. 78 b) nor abnormal behavior was detected in mice treated with 5Gy. Based on these results, a single 5 Gy dose of radiotherapy was usedin the combined treatment experiment.

Suppression of Primary Colon Carcinoma Tumor Progression by In-VivoExpression of TK Under Control of the PPE-1 (3×) Promoter andGanciclovir (GCV) Administration Combined with Local 5 Gy Radiotherapy:

100 male Balb/C mice aged 8 weeks were inoculated with CT-26 coloncarcinoma tumor cells. As soon as the tumor axis reached 4-6 mm, 10¹¹PFUs of the viral vectors [AdPPE-1(3×)-TK or AdCMV-TK] were injectedintravenously into the tail vein followed by 14 days of dailyintraperitoneal GCV injection (100 mg/kg body weight), where indicated.3 days post vector administration, the mice were irradiated with a local5 Gy dose. Tumor volume was assessed according to the formula V=π/6×α²×β(α is the short axis and β is the long axis). Upon sacrifice, the micewere photographed and tumor and liver specimens were harvested forhistological analysis.

AdPPE-1(3×)-TK+GCV+radiotherapy suppressed tumor progression compared tothe other treatment regimens. The duration of mean tumor suppression wasapproximately 2 weeks, which is compatible with the duration ofadenovirus activity. Mean tumor volume progression of theAdPPE-1(3×)-TK+GCV+radiotherapy treated group was smaller than that ofthe AdPPE-1(3×)-TK+GCV treated group (p=0.04) and the AdCMV-TK+GCVtreated group (p=0.008). Furthermore, mean tumor volume progression inthis group (AdPPE-1(3×)-TK+GCV+radiotherapy) was smaller than thecumulative mean tumor volume progression in all the other groups(p=0.0025), the cumulative mean tumor volume progression in allnon-irradiated groups (AdPPE-1(3×)-TK+GCV, Ad5CMV-TK+GCV, AdPPE-no GCVand saline+GCV; p=0.0005) and the cumulative mean tumor volumeprogression in the other irradiated groups (Ad5CMV-TK+GCV+radiotherapy,AdPPE-1(3×)-TK no GCV+radiotherapy and saline+GCV+radiotherapy; p=0.041)(FIG. 79 a,b). Radiotherapy significantly potentiated only theangiogenic endothelial cell transcription-targeted vector,AdPPE-1(3×)-TK, compared to the non-targeted vector, AdCMV-TK (p=0.04)(FIG. 79 c-f). Treatment regimens with all virus vectors wereineffective without radiotherapy.

Taken together, these results indicate the remarkable synergic tumorsuppressive effect of combined AdPPE-1(3×)-TK+GCV and radiotherapy onCT-26 colon cancer tumor development in vivo.

AdPPE-1(3×)-TK+GCV Combined with Radiotherapy Induces Massive TumorNecrosis:

In order to determine the mechanisms of the anti-tumorigenic effects ofcombined AdPPE-1(3×)-TK+GCV and radiotherapy, hematoxylin and eosinstaining was performed on tumor tissue. Tumor tissue was hypercellular,condensed and with a high mitotic index. Two elements were detected inall groups: necrosis and granulation tissue within the necrotic area.Tumors taken from mice treated with regimens that included radiationexhibited larger necrotic areas and granulated tissue than tumors takenfrom non-irradiated mice. In these groups, necrosis (FIG. 80 a) andgranulation tissue (FIG. 80 b) were mostly central. Mice treated withAdPPE-1(3×)-TK+GCV combined with radiotherapy exhibited the mostextensive necrosis and granulation tissue (FIGS. 80 a and 80 b),estimated at approximately 55%-80% of the specimen area (FIG. 80).Tumors taken from mice treated with AdPPE-1(3×)-TK+GCV withoutradiotherapy exhibited a relatively larger necrotic area than the othernon-irradiated groups (data not shown). The results suggest thatAdPPE-1(3×)-TK+GCV+radiotherapy induce massive central tumor necrosis,which is partially replaced by granulation tissue.

AdPPE-1(3×)-TK+GCV Combined with Radiotherapy Induce Endothelial Celland Massive Tumor Apoptosis:

To determine the character of cell death responsible for the inhibitoryeffect of AdPPE-1(3×)-TK+GCV and radiotherapy on colon cancer tumors,TUNEL and anti-caspase-3 staining were performed on tumor tissues inorder to demonstrate apoptotic cells. TUNEL staining demonstratedapoptotic tumor cells surrounding a central necrotic area in irradiatedgroups. More apoptotic tumor cells were detected in tumors taken frommice treated with AdPPE-1(3×)-TK+GCV combined with radiotherapy than inany other group (FIG. 30 a). The same apoptotic cell pattern wasdetected by anti-caspase-3 staining of the tumor sections. Furthermore,necrotic areas surrounded by apoptotic tumor cells (white arrows) had aserpentine shape and were unique in containing an increased vasculardensity (FIG. 81 b). Endothelial cells of blood vessels within apoptoticareas exhibited positive anti-caspase-3 staining (FIG. 82).

Taken together these results suggest that AdPPE-1(3×)-TK+GCV combinedwith radiotherapy induces massive tumor cell apoptosis surrounding anecrotic area in colon cancer tumors. Moreover, the increased angiogenicvessel density within tumor apoptotic areas, the shape of the necrosisand apoptotic areas and the existence of endothelial cell apoptosisindicate perivascular necrosis secondary to angiogenic tissue damage.

Combined AdPPE-1(3×)-TK+GCV Combined with Radiotherapy hasAnti-Angiogenic Effects in Suppression of Tumor Development In-Vivo:

CD-31 is a characteristic endothelial cell marker of angiogenesis. AntiCD-31 immuno-staining was performed on tumor tissues in order todemonstrate direct effects of the combined therapy on endothelial cells.Angiogenic vessels in sections of tumors taken from mice treated with aregimen that includes irradiation alone were short, without continuityor branching and with indistinct borders. Administration of vectoralone, without GCV, caused no abnormalities (FIG. 83 a), whileAdPPE-1(3×)-TK+GCV combined with radiotherapy demonstrated the mostextensive vascular abnormalities (FIG. 32 a). Hepatic blood vessels werenot affected (FIG. 83 b). The results indicate that administration ofAdPP1(3×)-TK+GCV, combined with radiotherapy induces extensive vasculardisruption in angiogenic vessels.

Systemic AdCMV-TK+GCV, but not AdPPE-1(3×) Administration InducesHepatotoxicity in Mice Bearing CT-26 Colon Cancer Tumors:

Since one of the major side effects of systemic administration ofadenovirus vectors is liver toxicity hematoxylin and eosin staining wasperformed on liver tissues from vector-treated, combination therapy andcontrol mice. Liver specimens in every treatment group exhibitedenlarged hepatocyte nuclei and Kupfer cell hyperplasia. The mostdistinctive changes were demonstrated in mice treated with AdCMV-TK+GCVwith or without radiotherapy (FIG. 84). No differences in plasma markersof liver function (liver enzymes SGOT, SGPT) or kidney function (urea,creatinine) were found between groups. It should be noted that hepaticendothelial cells were not affected by the vector AdPPE-1(3×)-TK+GCVcombined with radiotherapy (FIG. 84, right panel). The resultsdemonstrate that the adenovirus vector expressing HSV-TK controlled bythe CMV promoter is relatively hepatotoxic.

Taken together, these results suggest that AdPPE-1(3×)-TK+GCV is safefor intravenous administration. Moreover, the vector efficientlysuppresses slow growing primary tumor progression only in combinationwith non-toxic, locally-delivered radiotherapy is added. Without wishingto be limited to a single hypothesis, it seems likely that specificsuppression of tumor angiogenesis, via apoptosis, appears to be themechanism for tumor suppression. Moreover, the cytotoxic activity of theAdPPE-1 (3×)-TK vector is dependent upon administration of GCV andradiotherapy.

Example 36 Administration of Ganciclovir and TK Under Control of thePPE-1 (3×) Promoter in Combination with Radiotherapy SynergicEnhancement of Survival in Metastasizing Cancer In-Vivo

In order to evaluate the combined effect of the antiangiogenic activityof AdPPE-1(3×)-TK+GCV and single dose radiotherapy on long term survivalin cancer, systemic administration of the vector and GCV andradiotherapy in the rapidly metastasizing Lewis Lung Carcinoma model waschosen.

Local Single-Dose 5 Gy Radiotherapy is Non-Toxic and Sub-Therapeutic toC57Bl/6 Mice Bearing Lewis Lung Carcinoma Metastases:

35 C57BL/6 male mice aged 8 weeks were inoculated with LLC cells intothe left footpad. The foot was amputated under general anesthesia assoon as the primary tumor developed. 8 days post foot amputation asingle dose of radiotherapy aimed at the mouse's chest wall wasadministered under general anesthesia. Five radiation doses wereexamined: 0, 2, 50, 10 and 15 Gy. 3-4 weeks post primary tumor removalthe non-irradiated mice began to loose weight, which is a sign ofmetastatic disease. Mouse sacrifice was therefore scheduled for the28^(th) day post primary tumor removal. Mouse well-being was monitoreddaily by observation and weighing. 5 out of 6 mice treated with 15 Gydied within 5 days post-irradiation, without any signs of lungmetastasis. Mouse exclusion was as follows: one mouse was excludedbecause of a two-week delay in primary tumor development compared to theother groups. 3 mice died during follow-up and no autopsy was performed.Of the excluded mice, one mouse was excluded before enrollment, one fromthe non-treated group, one from the 2 Gy group and one to from the 5 Gygroup. The mean metastatic weight of mice treated with 10 Gy was lowerthan that of the other groups, but was only statistically different fromthe group treated with 5 Gy (p=0.001) (FIG. 85 a). As previouslymentioned, mice treated with 15 Gy radiation died within 5 days, withoutany trace of metastases. Mice treated with 10 Gy exhibited anon-significant transient weight reduction 10 days post-radiation (FIG.85 b). Since a single 5 Gy dose of radiotherapy was neither therapeutic(FIG. 85 a) nor toxic (FIG. 85 b), it was used in the combined treatmentexperiment.

Synergistic Suppression of Metastatic Disease in Murine Lung Carcinomawith Combined Sub-Therapeutic Radiotherapy and Expression of TK UnderControl of the PPE-1 (3×) Promoter and Ganciclovir (GCV) Administration:

180 male Balb/C mice aged 8 weeks were inoculated with LLC cells intothe left footpad. The foot was amputated under general anesthesia assoon as the primary tumor developed. 5 days post amputation, 10¹⁰ PFUsof vector [AdPPE-1(3×)-TK or AdCMV-TK] were injected into the tail vein,followed by 14 days of daily intraperitoneal injections of GCV (100mg/kg). 3 days post vector injection, a single 5 Gy dose of radiotherapyaimed at the mouse's chest wall was administered under generalanesthesia.

The mice were divided into 6 groups: 1. Ad5PPE-1(3×)-TK+GCV, 2.Ad5CMV-TK+GCV, 3. saline+GCV, 4. Ad5PPE-1(3×)-TK+GCV+radiotherapy, 5.Ad5CMV-TK+GCV+radiotherapy, and 6. saline+GCV+radiotherapy. Mouseexclusion: Four mice died soon after leg amputation, four mice wereexcluded since the primary tumor was too large for enrollment, 7 micewere excluded because of late primary tumor development, 12 mice diedwithout any trace of lung metastasis, 1 mouse was excluded because ofbilateral eye discharge. Of the excluded mice, 14 were excluded beforeenrollment, 2 were excluded from group 1, 2 from group 2, 2 from group3, 4 from group 4, 3 from group 5 and 1 from group 6.

Mice treated with AdPPE-1(3×)-TK+GCV+radiotherapy survived significantlylonger than the mice in any other treatment group (p=0.05) (FIG. 86 a).Moreover, radiotherapy significantly potentiated only the angiogenicendothelial cell transcription-targeted vector, AdPPE-1(3×)-TK, comparedto the non-targeted vector, AdCMV-TK (p=0.04) (FIG. 86 b-d). The resultsshow that combined treatment of systemically administered AdPPE-1(3×)-TKvector+GCV+single dose radiotherapy synergically prolongs survival inmetastatic disease.

Example 37 Dual Therapy with Fas and TNFR Chimeric Gene Under Control ofthe PPE-1 (3×) Promoter Synergic Enhancement of Endothelial CellSpecificity In-Vitro with Doxorubicin

In order to test the efficacy of combined chemotherapy and angiogenicendothelial-specific expression of “suicide genes” other than HSV/TK,AdPPE-1 (3×)-Fas-c, having a PPE-1(3×) promoter in combination withFas-chimera (Fas-c, see detailed description hereinabove) wasadministered to BAE cells alone, and in combination with theanthracycline glycoside doxorubicin (DOX).

Apoptosis, as measured by cell survival (% viability, assessed bycrystal violet staining) of BAE cells, was significantly greater in micetreated with AdPPE-1 (3×)-Fas-c+DOX than with either AdPPE-1 (3×)-Fas-cor DOX alone (FIG. 91).

These results indicate that the PPE-1 (3×) promoter can be used todirect efficient, endothelium-specific expression of additionaltherapeutic gene constructs, and that the combination of PPE-1 (3×)dependent, apoptosis-inducing Fas-c expression and chemotherapy resultsin highly efficient synergic endothelial apoptosis.

Example 38 Conditionally Replicating Adenovirus Vectors Materials andExperimental Methods

Cell Culture:

Bovine Aortic Endothelial cells (BAEC) and Human Normal skinfibroblasts—NSF cell-lines are cultured in low glucose DMEM containing10% heat inactivated FCS, 100 μg/ml penicillin and 100 μg/mlstreptomycin. HeLa (Human cervix epithelial adenocarcinoma), Lewis LungCarcinoma cells (D122-96) and 293 (human embryonic kidney) cell-linesare cultured in high glucose DMEM containing 10% heat inactivated FCS,100 μg/ml penicillin, 100 μg/ml streptomycin. Human UmbilicalEndothelial Cells—HUVEC (Cambrex Bio Science Walkersville, Inc.) arecultured in EGM-2 Bullet kit (Clonetics, Bio-Whittaker, Inc., MD, USA).Human lung carcinoma cell line (A549) are cultured in MEM containing 10%heat inactivated FCS, 100 μg/ml penicillin and 100 μg/ml streptomycin.All cells are grown in 37° C., 5% CO₂, humidified atmosphere.

Plasmids and Viral Vectors Construction:

Plasmid Cloning:

The cDNA of firefly luciferase was sub-cloned into the multiple cloningsite of pcDNAIII expression plasmid (containing CMV promoter region,Invitrogen), and into pPACPPE-1.p1pA, which contains PPE1-3× promoterand parts of the adenovirus-5 DNA sequence. A third plasmid was clonedby deleting the first intron of PPE-1 promoter from pPACPPE-1.p1pAplasmid. The three plasmids were previously cloned in our lab and wereused in cell culture transfections.

Replication Deficient Vectors Cloning:

The cDNA of FAS-chimera was sub-cloned into pPACPPE-1.p1pA andpPACCMV.p1pA plasmids. These plasmids were co-transfected with pJM17that contains most of the adenovirus-5 genome and were co-transfectedwith calcium phosphate method into 293 human embryonic kidney cell-line(ATCC). This cell-line was designed to include the E1 gene that isnecessary for viral replication but is not included in the pPAC.p1pA orpJM17 plasmids. The plasmids undergo homologous recombination within thecells, and after approximately two weeks recombinant viruses are formedand start to replicate and finally cause cell lysis. Viral colonies areseparated and propagated and their accurate insert orientation isverified by PCR. The replication deficient vectors were previouslyprepared by conventional prior art cloning techniques.

Conditionally Replicating Adenovirus (CRAD) Construction:

The CRADs were constructed using the AdEasy method (Stratagene, La JollaCalif.). PShuttle-MK, a plasmid containing parts of the adenovirus-5 DNAsequence, has been modified as follows: the multiple cloning site andright arm in pShuttle (Stratagene, La Jolla, Calif.) were replaced byMidkine (mk) promoter and the consecutive adenoviral E1 region. Later,the MK promoter was replaced by PPE1-3× without intron. A second plasmidwas constructed by subcloning IRES sequence (from p IRES-EYFP plasmid,BD Biosciences) and FAS-chimera cDNA between the promoter and E1. IRESpermits translation of two proteins from the same transcript. Theresultant two shuttles were linearized with PmeI digestion andsubsequently transformed into Escherichia coli BJ5183ADEASY-1(Stratagene). This type of bacteria has already been transformed withpADEASY-1 plasmid, which contains most of the adenovirus-5 sequence,except E1 and E3 gene regions. The plasmids undergo homologousrecombination within the bacteria (between pShuttle and pADEASY-1), thuscreating the complete vector genome. The recombinants were later Paddigested and transfected with calcium phosphate method into 293 humanembryonic kidney cell-line (ATCC). The rest of the procedure is asdescribed for the replication deficient vectors.

The positive control virus CMV-E1 was constructed by subcloning thegeneral promoter CMV (cytomegalovirus) before the E1 gene. CMV-E1 virusis ubiquitous and has no specificity to endothelial cells.

The following replication deficient vectors and CRADs were constructedaccording to the abovementioned methods:

Replication Deficient Vectors:

PPE-1(3×)-FAS, CMV-FAS, CMV-LUC (LUC—abbreviation for firefly luciferasereporter gene), PPE-1(3×)-LUC.

CRADs:

PPE-1(3×)-CRAD, PPE-1(3×)-Fas-CRAD, CMV-E1

Transfection Experiments:

BAEC and HeLa cells were cultured in 24-wells plates to 60-70%confluence. Cotransfection was done using 0.4 μg/well of expressionconstruct and 0.04 μg/well of pEGFP-C1 vector (CLONTECH, Palo Alto,Calif.) as a control for transfection efficiency. Lipofectamine andLipofectamine plus (Invitrogen, Carlsbad, Calif.) were used fortransfection. After 3 hours of incubation at 37° C., transfectionmixture was replaced with growth medium.

Transduction Experiments:

Vectors (PPE-FAS, CMV-FAS, CMV-LUC, PPE-LUC) were diluted with theinfection growth media (Contains 2% FCS instead of 10% in normal growthmedia) in order to reach to multiplicity of infection (moi) of 10, 100,1000, 10000. The multiplicity of infection was calculated as the numberof viruses per target cell. Target cells (BAEC and 293) had been seeded24 hours before transduction. At the transduction day, cell's growthmedia was replaced with solution containing the viruses in the desiredmoi's mixed in 0.1 or 2 ml infection media for 96 wells plate or 60 mmplate, respectively. The cells were incubated for 4 hours, followed bythe addition of fresh medium to the transduced cells.

Evaluations of vector replication and apoptotic induction is by PFUtitering (see below) and ApoPercentage kit (Accurate Chemical, Westbury,N.Y.), respectively. Crystal Violet staining was also used to evaluatethe amount of cells attached to the plate's surface, as an indicator forcell viability.

Testing the Viral Titer—Plaque Forming Unit Assay (PFU):

The viral stocks were titered and stored at −80° C. Sub-confluent (80%)culture of 293 cells was infected for 2 hours by the viral vectordiluted with the infection media for serial dilutions (10⁻²-10⁻¹³).After two hours the medium was washed by PBS and was replaced by agaroverlay. The highest dilution in which plaques are apparent afterapproximately 2 weeks, is considered the concentration in units ofPFU/ml (PFU—plaque forming units).

Results

Cytotoxic Gene Expression Enhances Adenovirus Replication:

In order to test the influence of apoptotic induction on viralreplication, CMV-FAS replication was tested in the 293 (human embryonickidney) cell-line. In this cell-line the virus can induce apoptosis byFAS-c or cell lysis as a result of its replication. Early (a few hoursafter viral infection) apoptosis might interfere with viral replication,while late apoptosis (a few days after viral infection) might enhanceviral spread.

In order to test the ability of CMV-FAS to induce apoptosis, BAEC weretransduced, and cell apoptosis was evaluated by ELISA-crystal violetassay of viability (FIG. 89). CMV-FAS at higher concentration (10000moi) induced apoptosis without the activating ligand (TNF-α), while inlower concentrations there was a need for addition of the ligand inorder to induce apoptosis.

CMV-FAS spread from cell to cell was assayed by plaque development in293 cells. Plaque development occurred at a higher rate with the CMV-FASvector, compared to a non-apoptosis inducing vector—CMV-LUC, as observed(FIGS. 88 and 89) according to the rate of plaque development and sizeof plaques.

The ability of PPE1-3× promoter, with and without the intron, to induceRNA transcription, was assessed by the luciferase reporter gene (notshown). No significant differences were observed.

These results indicate that replication of adenovirus vectors, such asthe angiogenic, endothelial-specific viral construct AdPPE-1(3×)described hereinabove, bearing apoptosis-inducing “killer” genes such asFAS, can be enhanced by the additional apoptotic lysis of the hostcells.

Example 39 PPE-1 (3×) Control of VEGF Expression EnhancesNeovascularization and Survival of Engineered Tissues

In order to study the effect of expression of VEGF under the control ofendothelin promoter on the vascularization of engineered tissueconstruct in vitro and in vivo, cells were infected withAd5PPEC-1-3×VEGF and constructs were analyzed to see the effect onvascularization.

FIG. 91 a shows that infection of the cells with Ad5PPEC-1-3×VEGF has aninductive effect on number and size of vessels-like structures formed inthe engineered constructs. Constructs were grown with or without VEGFsupplementation to the medium (50 ng/ml). Parallel constructs wereinfected with Ad5PPEC-1−3×VEGF viruses or control GFP adenoviruses (for4 hours). Following 2 weeks in culture the constructs were fixed,embedded, sectioned and stained.

Comparing between addition of VEGF to the medium and infection the cellswith Ad5PPEC-1-3×VEGF, a 4 to 5-fold increase in the number of vesselsand percentages of vessel area in the samples treated withAd5PPEC-1-3×VEGF virus was found (FIG. 91 a).

In in-vivo studies, three different models were used to analyzesurvival, differentiation, integration and vascularization of theimplant in vivo. These models included (i) Subcutaneous Implantation inthe back of SCID mice, (ii) Implantation into the quadriceps muscle ofnude rats, and (iii) Replacement of anterior abdominal muscle segment ofnude mice with the construct.

The constructs were permeated with host blood vessels. Constructsinfected with Ad5PPEC-1-3×VEGF virus showed an increase in vesselstructures compared to control constructs.

To evaluate tissue-engineered construct survival and integration invivo, we employed a luciferase-based imaging system. The in vivo imagingsystem (IVIS) works by detecting light generated by the interaction ofsystemically administered luciferin with locally produced luciferase.Constructs were infected with Adeno Associated Virus (AAV) vectorencoding luciferase for 48 hours prior to transplantation. Theconstructs were then placed in situ in the anterior abdominal musclewalls of nude mice. AAV-Luciferase was injected into the left lowerextremity of each mouse at the time of surgery to serve as a positivecontrol. Three-four weeks following surgery, the mice received luciferinto assess perfusion to the tissue-engineered construct.

Constructs infected with Ad5PPEC-1-3×VEGF (and infected later withAAV-luciferase) had higher signal than control constructs infected withAAV-luciferase only (results not shown). Taken together, these resultssuggest that in vitro infection with Ad5PPEC-1-3×VEGF can improvesurvival and vascularization of implanted engineered tissue constructs.

Example 40 In-Vivo Activation of PPE-1(3×) Promoter by AntiangiogenicTreatment

A common response of many tissues to repression of angiogenesis is theupregulation of endogenous angiogenic pathways, in response to complexsignaling generated by the auto-regulated autocrine feedback loopsgoverning vascular homeostasis (see Hahn et al, Am J Med 1993, 94:13S-19S, and Schramek et al, Senim Nephrol 1995; 15:195-204). In order todetermine how such a mechanism would effect the expression of nucleicacid sequences under control of the PPE-1 (3×) promoter, the in-vivolevel of luminescence was measured in tissues in transgenic micetransformed with a nucleic acid construct of the present inventionincluding the luciferase (LUC) gene under PPE-1(3×) control [PPE-1(3×)-LUC], with and without administration of the potent antiangiogenicdrug Bosentan. Bosentan (Tracleer™) is a dual endothelin receptor (ETAand ETB) antagonist presently clinically approved for a variety ofindications, most importantly pulmonary arterial hypertension andpulmonary fibrosis.

Transgenic mice bearing the PPE-1(3×)-LUC construct of the presentinvention were produced by cloning methods well known in the art, asdescribed in detail hereinabove. 10 week old PPE-1(3×)-Luc transgenicmice, (n=5 in each group) were either fed orally with chow diet or chowdiet with 100 mg/kg/day Bosentan for 30 days. Mice were sacrificed onthe last day of treatment and organs, the organs of the mice removed formeasurement of luminescence intensity, as described in the Methodssection hereinabove.

FIG. 94 shows that the PPE-1 (3×) promoter confers tissue specificover-expression of the recombinant gene in the transgenic mice. Organshaving normally greater endothelin activity, such as heart and aorta,and to a lesser extent, brain, trachea and lungs, showed an increasedluminescence intensity, as compared with liver or kidney. In mostorgans, however, luminescence intensity was remarkably enhanced (up to40% in heart tissue) by Bosentan administration (FIG. 94), thusindicating that endothelin receptor antagonists, in particular, andinhibitors of angiogenesis in general, can activate the endothelialspecific promoters of the present invention, and induce furtherenhancement of expression of transgenes under PPE-1 (3×) transcriptionalcontrol, in a tissue specific manner.

Example 41 Transgenes Expressed In-Vivo Under Control of the PPE-1(3×)Promoter are not Immunogenic

As described hereinabove, gene therapy, as other long-term therapeuticmodalities, is often complicated by endogenous host immune reaction tocontinued exposure to expressed transgenic protein. Immune stimulationby the transgenic protein can cause reduced efficacy of treatment,inflammation, and sometimes severe side effects. In order to test thehost immune response to transgenes expressed using the cis reactingregulatory element of the present invention, antibody titers againstadenoviral hexone and TNF-R1 were assayed in mice bearing LLCmicrometastases, and treated with vectors bearing the Fas-TNF-R1 chimera(Ad5PPE-1(3×) Fas-c and Ad5CMV Fas-c), or the LUC reporter gene(Ad5PPE-1(3×) Luc) (6 mice per group). Control mice were treated withsaline.

Vectors were injected 3 times, at an interval of 5 days betweeninjection. Mice were sacrificed 10 days after last vector injection, fordetermination of levels of antibodies against the adenovirus and againsthuman TNF-R1, the protein expressed by the transgene inserted, using anELISA assay.

Unexpectedly, the levels of antibodies against human TNF-R1 were foundto be below the level of detection in Ad5-PPE(3×)-Fas-c treated mice,whereas these levels were relatively high in the mice treated with thenon-specific Ad5-CMV-fas vector (FIG. 95 b). Antibody titers against theadenoviral hexone antigen were similar among the differentvirus-injected groups (FIG. 95 a). These results indicate thattransgenes expressed using the PPE-1(3×) construct of the presentinvention are well tolerated by the host immune system, irrespective ofphylogenetic proximity.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims. All publications, patents and patentapplications mentioned in this specification are herein incorporated intheir entirety by reference into the specification, to the same extentas if each individual publication, patent or patent application wasspecifically and individually indicated to be incorporated herein byreference. In addition, citation or identification of any reference inthis application shall not be construed as an admission that suchreference is available as prior art to the present invention.

1. A method of inhibiting angiogenesis in an endothelial tissue of asubject in need thereof, the method comprising administering to saidsubject a nucleic acid construct comprising: (a) an isolatedpolynucleotide comprising an enhancer element including at least onecopy of the sequence set forth in SEQ ID NO:8; (b) a promoter functionalin eukaryotic cells; and (c) a nucleic acid sequence encoding anapoptosis inducing factor under the control of said promoter, whereinsaid subject is being treated with radiation therapy.
 2. The method ofclaim 1, wherein said radiation therapy is administered concomitantlywith said nucleic acid construct.
 3. The method of claim 1, wherein saidnucleic acid construct is administered prior to treatment with saidradiation therapy.
 4. The method of claim 1, wherein said apoptosisinducing factor is a pro-apoptotic gene.
 5. The method of claim 1,wherein said enhancer element further includes at least one copy of thesequence set forth in SEQ ID NO:6.
 6. The method of claim 1, whereinsaid enhancer element includes one copy of the sequence set forth in SEQID NO: 8 and at least two copies of the sequence set forth in SEQ ID NO:6.
 7. The method of claim 1, wherein said enhancer element is as setforth in SEQ ID NO:
 7. 8. The method of claim 1, wherein said promoteris an endothelial specific promoter element.
 9. The method of claim 8,wherein said endothelial specific promoter element comprises at leastone copy of the PPE-1 promoter.
 10. The nucleic acid construct of claim9, wherein said PPE-1 promoter element comprises the nucleic acidsequence as set forth in SEQ ID NO:
 1. 11. The nucleic acid construct ofclaim 8, wherein said endothelial specific promoter element comprises atleast one copy of the PPE-1-3× promoter.
 12. The method of claim 1,wherein said nucleic acid construct further comprises a hypoxia responseelement.
 13. The method of claim 12, wherein said hypoxia responseelement includes at least one copy of the sequence set forth in SEQ IDNO:
 5. 14. The method of claim 1, further comprising an adenovirusvector.
 15. The nucleic acid construct of claim 14, wherein saidadenovirus vector is an adenovirus serotype 5 vector.
 16. The method ofclaim 15, wherein said tissue is a tumor mass.
 17. A method ofinhibiting angiogenesis in an endothelial tissue of a subject in needthereof, the method comprising administering to said subject arecombinant adenovirus vector comprising: (a) an isolated polynucleotidecomprising an enhancer element including at least one copy of thesequence set forth in SEQ ID NO:7; (b) a PPE-1 promoter functional ineukaryotic cells as set forth in SEQ ID NO: 1; (c) a nucleic acidsequence encoding an apoptosis inducing factor under the control of saidpromoter; and (d) a hypoxia response element as set forth in SEQ ID NO:5, wherein said adenovirus vector is an Ad serotype 5 vector and whereinsaid subject is being treated with radiation therapy.
 18. The method ofclaim 17, wherein said radiation therapy is administered concomitantlywith said nucleic acid construct.
 19. The method of claim 17, whereinsaid nucleic acid construct is administered prior to treatment with saidradiation therapy.
 20. The method of claim 17, wherein said apoptosisinducing element is a pro-apoptotic gene.
 21. The method of claim 17,wherein said tissue is a tumor mass.